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• Javascript object list sorting by object property

  - by Constructor

  I need to do this: (sorry not in javascript syntax-still learning object language :) ) object=car attibutes:top-speed, brand.... now I want to sort the list of those cars in order by top-speed, brand... How do I do this (please note the solution must be javascript only, no php or other stuff) ?

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• How do I use a .NET class in VBA? Syntax help!

  - by Jordan S

  ok I have couple of .NET classes that I want to use in VBA. So I must register them through COM and all that. I think I have the COM registration figured out (finally) but now I need help with the syntax of how to create the objects. Here is some pseudo code showing what I am trying to do. EDIT: Changed Attached Objects to return an ArrayList instead of a List The .NET classes look like this... public class ResourceManagment { public ResourceManagment() { // Default Constructor } public static List<RandomObject> AttachedObjects() { ArrayList list = new ArrayList(); return list; } } public class RandomObject { // public RandomObject(int someParam) { } } OK, so this is what I would like to do in VBA (demonstrated in C#) but I don't know how... public class VBAClass { public void main() { ArrayList myList = ResourceManagment.AttachedObjects(); foreach(RandomObject x in myList) { // Do something with RandomObject x like list them in a Combobox } } } One thing to note is that RandomObject does not have a public default constructor. So I can not create an instance of it like Dim x As New RandomObject. MSDN says that you can not instantiate an object that doesn't have a default constructor through COM but you can still use the object type if it is returned by another method... Types must have a public default constructor to be instantiated through COM. Managed, public types are visible to COM. However, without a public default constructor (a constructor without arguments), COM clients cannot create an instance of the type. COM clients can still use the type if the type is instantiated in another way and the instance is returned to the COM client. You may include overloaded constructors that accept varying arguments for these types. However, constructors that accept arguments may only be called from managed (.NET) code. Added: Here is my attempt in VB: Dim count As Integer count = 0 Dim myObj As New ResourceManagment For Each RandomObject In myObj.AttachedObjects count = count + 1 Next RandomObject

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• How can I improve this design?

  - by klausbyskov

  Let's assume that our system can perform actions, and that an action requires some parameters to do its work. I have defined the following base class for all actions (simplified for your reading pleasure): public abstract class BaseBusinessAction<TActionParameters> : where TActionParameters : IActionParameters { protected BaseBusinessAction(TActionParameters actionParameters) { if (actionParameters == null) throw new ArgumentNullException("actionParameters"); this.Parameters = actionParameters; if (!ParametersAreValid()) throw new ArgumentException("Valid parameters must be supplied", "actionParameters"); } protected TActionParameters Parameters { get; private set; } protected abstract bool ParametersAreValid(); public void CommonMethod() { ... } } Only a concrete implementation of BaseBusinessAction knows how to validate that the parameters passed to it are valid, and therefore the ParametersAreValid is an abstract function. However, I want the base class constructor to enforce that the parameters passed are always valid, so I've added a call to ParametersAreValid to the constructor and I throw an exception when the function returns false. So far so good, right? Well, no. Code analysis is telling me to "not call overridable methods in constructors" which actually makes a lot of sense because when the base class's constructor is called the child class's constructor has not yet been called, and therefore the ParametersAreValid method may not have access to some critical member variable that the child class's constructor would set. So the question is this: How do I improve this design? Do I add a Func<bool, TActionParameters> parameter to the base class constructor? If I did: public class MyAction<MyParameters> { public MyAction(MyParameters actionParameters, bool something) : base(actionParameters, ValidateIt) { this.something = something; } private bool something; public static bool ValidateIt() { return something; } } This would work because ValidateIt is static, but I don't know... Is there a better way? Comments are very welcome.

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• Inheritance of closure objects and overriding of methods

  - by bobikk

  I need to extend a class, which is encapsulated in a closure. This base class is following: var PageController = (function(){ // private static variable var _current_view; return function(request, new_view) { ... // priveleged public function, which has access to the _current_view this.execute = function() { alert("PageController::execute"); } } })(); Inheritance is realised using the following function: function extend(subClass, superClass){ var F = function(){ }; F.prototype = superClass.prototype; subClass.prototype = new F(); subClass.prototype.constructor = subClass; subClass.superclass = superClass.prototype; StartController.cache = ''; if (superClass.prototype.constructor == Object.prototype.constructor) { superClass.prototype.constructor = superClass; } } I subclass the PageController: var StartController = function(request){ // calling the constructor of the super class StartController.superclass.constructor.call(this, request, 'start-view'); } // extending the objects extend(StartController, PageController); // overriding the PageController::execute StartController.prototype.execute = function() { alert('StartController::execute'); } Inheritance is working. I can call every PageController's method from StartController's instance. However, method overriding doesn't work: var startCont = new StartController(); startCont.execute(); alerts "PageController::execute". How should I override this method?

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• Inereritance of clousure objects and overriding of methods

  - by bobikk

  I need to extend a class, which is encapsulated in a closure. This base class is following: var PageController = (function(){ // private static variable var _current_view; return function(request, new_view) { ... // priveleged public function, which has access to the _current_view this.execute = function() { alert("PageController::execute"); } } })();` Inheritance is realised using the following function: function extend(subClass, superClass){ var F = function(){ }; F.prototype = superClass.prototype; subClass.prototype = new F(); subClass.prototype.constructor = subClass; subClass.superclass = superClass.prototype; StartController.cache = ''; if (superClass.prototype.constructor == Object.prototype.constructor) { superClass.prototype.constructor = superClass; } } I subclass the PageController: var StartController = function(request){ // calling the constructor of the super class StartController.superclass.constructor.call(this, request, 'start-view'); } // extending the objects extend(StartController, PageController); // overriding the PageController::execute StartController.prototype.execute = function() { alert('StartController::execute'); } Inheritance is working. I can call every PageController's method from StartController's instance. However, method overriding doesn't work: var startCont = new StartController(); startCont.execute(); alerts "PageController::execute". How should I override this method?

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• Any workarounds for non-static member array initialization?

  - by TomiJ

  In C++, it's not possible to initialize array members in the initialization list, thus member objects should have default constructors and they should be properly initialized in the constructor. Is there any (reasonable) workaround for this apart from not using arrays? [Anything that can be initialized using only the initialization list is in our application far preferable to using the constructor, as that data can be allocated and initialized by the compiler and linker, and every CPU clock cycle counts, even before main. However, it is not always possible to have a default constructor for every class, and besides, reinitializing the data again in the constructor rather defeats the purpose anyway.] E.g. I'd like to have something like this (but this one doesn't work): class OtherClass { private: int data; public: OtherClass(int i) : data(i) {}; // No default constructor! }; class Foo { private: OtherClass inst[3]; // Array size fixed and known ahead of time. public: Foo(...) : inst[0](0), inst[1](1), inst[2](2) {}; }; The only workaround I'm aware of is the non-array one: class Foo { private: OtherClass inst0; OtherClass inst1; OtherClass inst2; OtherClass *inst[3]; public: Foo(...) : inst0(0), inst1(1), inst2(2) { inst[0]=&inst0; inst[1]=&inst1; inst[2]=&inst2; }; }; Edit: It should be stressed that OtherClass has no default constructor, and that it is very desirable to have the linker be able to allocate any memory needed (one or more static instances of Foo will be created), using the heap is essentially verboten. I've updated the examples above to highlight the first point.

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• Unity and Object Creation

  - by William

  I am using unity as my IoC container. I am trying to implement a type of IProviderRepository. The concrete implementation has a constructor that accepts a type of IRepository. When I remove the constructor parameter from the concrete implementation everything works fine. I am sure the container is wired correctly. When I try to create the concrete object with the constructor I receive the following error: "The current build operation (build key Build Key[EMRGen.Infrastructure.Data.IRepository1[EMRGen.Model.Provider.Provider], null]) failed: The current type, EMRGen.Infrastructure.Data.IRepository1[EMRGen.Model.Provider.Provider], is an interface and cannot be constructed. Are you missing a type mapping? (Strategy type BuildPlanStrategy, index 3)". Is it possible to achieve the above mention functionality with Unity? Namely have Unity infer a concrete type from the Interface and also inject the constructor of the concrete type with the appropriate concrete object based on constructor parameters. Below is sample of my types defined in Unity and a skeleton class listing for what I want to achieve. IProviderRepository is implemented by ProviderRepository which has a constructor that expects a type of IRepository. <typeAlias alias="ProviderRepositoryInterface" type="EMRGen.Model.Provider.IProviderRepository, EMRGen.Model" /> <typeAlias alias="ProviderRepositoryConcrete" type="EMRGen.Infrastructure.Repositories.Providers.ProviderRepository, EMRGen.Infrastructure.Repositories" /> <typeAlias alias="ProviderGenericRepositoryInterface" type="EMRGen.Infrastructure.Data.IRepository`1[[EMRGen.Model.Provider.IProvider, EMRGen.Model]], EMRGen.Infrastructure" /> <typeAlias alias="ProviderGenericRepositoryConcrete" type="EMRGen.Infrastructure.Repositories.EntityFramework.ApplicationRepository`1[[EMRGen.Model.Provider.Provider, EMRGen.Model]], EMRGen.Infrastructure.Repositories" /> <!-- Provider Mapping--> <typeAlias alias="ProviderInterface" type="EMRGen.Model.Provider.IProvider, EMRGen.Model" /> <typeAlias alias="ProviderConcrete" type="EMRGen.Model.Provider.Doctor, EMRGen.Model" /> //Illustrate the call being made inside my class public class PrescriptionService { PrescriptionService() { IUnityContainer uc = UnitySingleton.Instance.Container; UnityServiceLocator unityServiceLocator = new UnityServiceLocator(uc); ServiceLocator.SetLocatorProvider(() => unityServiceLocator); IProviderRepository pRepository = ServiceLocator.Current.GetInstance<IProviderRepository>(); } } public class GenericRepository<IProvider> : IRepository<IProvider> { } public class ProviderRepository : IProviderRepository { private IRepository<IProvider> _genericProviderRepository; //Explict public default constructor public ProviderRepository(IRepository<IProvider> genericProviderRepository) { _genericProviderRepository = genericProviderRepository; } }

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• Flow-Design Cheat Sheet &ndash; Part I, Notation

  - by Ralf Westphal

  You want to avoid the pitfalls of object oriented design? Then this is the right place to start. Use Flow-Oriented Analysis (FOA) and –Design (FOD or just FD for Flow-Design) to understand a problem domain and design a software solution. Flow-Orientation as described here is related to Flow-Based Programming, Event-Based Programming, Business Process Modelling, and even Event-Driven Architectures. But even though “thinking in flows” is not new, I found it helpful to deviate from those precursors for several reasons. Some aim at too big systems for the average programmer, some are concerned with only asynchronous processing, some are even not very much concerned with programming at all. What I was looking for was a design method to help in software projects of any size, be they large or tiny, involing synchronous or asynchronous processing, being local or distributed, running on the web or on the desktop or on a smartphone. That´s why I took ideas from all of the above sources and some additional and came up with Event-Based Components which later got repositioned and renamed to Flow-Design. In the meantime this has generated some discussion (in the German developer community) and several teams have started to work with Flow-Design. Also I´ve conducted quite some trainings using Flow-Orientation for design. The results are very promising. Developers find it much easier to design software using Flow-Orientation than OOAD-based object orientation. Since Flow-Orientation is moving fast and is not covered completely by a single source like a book, demand has increased for at least an overview of the current state of its notation. This page is trying to answer this demand by briefly introducing/describing every notational element as well as their translation into C# source code. Take this as a cheat sheet to put next to your whiteboard when designing software. However, please do not expect any explanation as to the reasons behind Flow-Design elements. Details on why Flow-Design at all and why in this specific way you´ll find in the literature covering the topic. Here´s a resource page on Flow-Design/Event-Based Components, if you´re able to read German. Notation Connected Functional Units The basic element of any FOD are functional units (FU): Think of FUs as some kind of software code block processing data. For the moment forget about classes, methods, “components”, assemblies or whatever. See a FU as an abstract piece of code. Software then consists of just collaborating FUs. I´m using circles/ellipses to draw FUs. But if you like, use rectangles. Whatever suites your whiteboard needs best.   The purpose of FUs is to process input and produce output. FUs are transformational. However, FUs are not called and do not call other FUs. There is no dependency between FUs. Data just flows into a FU (input) and out of it (output). From where and where to is of no concern to a FU.   This way FUs can be concatenated in arbitrary ways:   Each FU can accept input from many sources and produce output for many sinks:   Flows Connected FUs form a flow with a start and an end. Data is entering a flow at a source, and it´s leaving it through a sink. Think of sources and sinks as special FUs which conntect wires to the environment of a network of FUs.   Wiring Details Data is flowing into/out of FUs through wires. This is to allude to electrical engineering which since long has been working with composable parts. Wires are attached to FUs usings pins. They are the entry/exit points for the data flowing along the wires. Input-/output pins currently need not be drawn explicitly. This is to keep designing on a whiteboard simple and quick.   Data flowing is of some type, so wires have a type attached to them. And pins have names. If there is only one input pin and output pin on a FU, though, you don´t need to mention them. The default is Process for a single input pin, and Result for a single output pin. But you´re free to give even single pins different names.   There is a shortcut in use to address a certain pin on a destination FU:   The type of the wire is put in parantheses for two reasons. 1. This way a “no-type” wire can be easily denoted, 2. this is a natural way to describe tuples of data.   To describe how much data is flowing, a star can be put next to the wire type:   Nesting – Boards and Parts If more than 5 to 10 FUs need to be put in a flow a FD starts to become hard to understand. To keep diagrams clutter free they can be nested. You can turn any FU into a flow: This leads to Flow-Designs with different levels of abstraction. A in the above illustration is a high level functional unit, A.1 and A.2 are lower level functional units. One of the purposes of Flow-Design is to be able to describe systems on different levels of abstraction and thus make it easier to understand them. Humans use abstraction/decomposition to get a grip on complexity. Flow-Design strives to support this and make levels of abstraction first class citizens for programming. You can read the above illustration like this: Functional units A.1 and A.2 detail what A is supposed to do. The whole of A´s responsibility is decomposed into smaller responsibilities A.1 and A.2. FU A thus does not do anything itself anymore! All A is responsible for is actually accomplished by the collaboration between A.1 and A.2. Since A now is not doing anything anymore except containing A.1 and A.2 functional units are devided into two categories: boards and parts. Boards are just containing other functional units; their sole responsibility is to wire them up. A is a board. Boards thus depend on the functional units nested within them. This dependency is not of a functional nature, though. Boards are not dependent on services provided by nested functional units. They are just concerned with their interface to be able to plug them together. Parts are the workhorses of flows. They contain the real domain logic. They actually transform input into output. However, they do not depend on other functional units. Please note the usage of source and sink in boards. They correspond to input-pins and output-pins of the board.   Implicit Dependencies Nesting functional units leads to a dependency tree. Boards depend on nested functional units, they are the inner nodes of the tree. Parts are independent, they are the leafs: Even though dependencies are the bane of software development, Flow-Design does not usually draw these dependencies. They are implicitly created by visually nesting functional units. And they are harmless. Boards are so simple in their functionality, they are little affected by changes in functional units they are depending on. But functional units are implicitly dependent on more than nested functional units. They are also dependent on the data types of the wires attached to them: This is also natural and thus does not need to be made explicit. And it pertains mainly to parts being dependent. Since boards don´t do anything with regard to a problem domain, they don´t care much about data types. Their infrastructural purpose just needs types of input/output-pins to match.   Explicit Dependencies You could say, Flow-Orientation is about tackling complexity at its root cause: that´s dependencies. “Natural” dependencies are depicted naturally, i.e. implicitly. And whereever possible dependencies are not even created. Functional units don´t know their collaborators within a flow. This is core to Flow-Orientation. That makes for high composability of functional units. A part is as independent of other functional units as a motor is from the rest of the car. And a board is as dependend on nested functional units as a motor is on a spark plug or a crank shaft. With Flow-Design software development moves closer to how hardware is constructed. Implicit dependencies are not enough, though. Sometimes explicit dependencies make designs easier – as counterintuitive this might sound. So FD notation needs a ways to denote explicit dependencies: Data flows along wires. But data does not flow along dependency relations. Instead dependency relations represent service calls. Functional unit C is depending on/calling services on functional unit S. If you want to be more specific, name the services next to the dependency relation: Although you should try to stay clear of explicit dependencies, they are fundamentally ok. See them as a way to add another dimension to a flow. Usually the functionality of the independent FU (“Customer repository” above) is orthogonal to the domain of the flow it is referenced by. If you like emphasize this by using different shapes for dependent and independent FUs like above. Such dependencies can be used to link in resources like databases or shared in-memory state. FUs can not only produce output but also can have side effects. A common pattern for using such explizit dependencies is to hook a GUI into a flow as the source and/or the sink of data: Which can be shortened to: Treat FUs others depend on as boards (with a special non-FD API the dependent part is connected to), but do not embed them in a flow in the diagram they are depended upon.   Attributes of Functional Units Creation and usage of functional units can be modified with attributes. So far the following have shown to be helpful: Singleton: FUs are by default multitons. FUs in the same of different flows with the same name refer to the same functionality, but to different instances. Think of functional units as objects that get instanciated anew whereever they appear in a design. Sometimes though it´s helpful to reuse the same instance of a functional unit; this is always due to valuable state it holds. Signify this by annotating the FU with a “(S)”. Multiton: FUs on which others depend are singletons by default. This is, because they usually are introduced where shared state comes into play. If you want to change them to be a singletons mark them with a “(M)”. Configurable: Some parts need to be configured before the can do they work in a flow. Annotate them with a “(C)” to have them initialized before any data items to be processed by them arrive. Do not assume any order in which FUs are configured. How such configuration is happening is an implementation detail. Entry point: In each design there needs to be a single part where “it all starts”. That´s the entry point for all processing. It´s like Program.Main() in C# programs. Mark the entry point part with an “(E)”. Quite often this will be the GUI part. How the entry point is started is an implementation detail. Just consider it the first FU to start do its job.   Patterns / Standard Parts If more than a single wire is attached to an output-pin that´s called a split (or fork). The same data is flowing on all of the wires. Remember: Flow-Designs are synchronous by default. So a split does not mean data is processed in parallel afterwards. Processing still happens synchronously and thus one branch after another. Do not assume any specific order of the processing on the different branches after the split.   It is common to do a split and let only parts of the original data flow on through the branches. This effectively means a map is needed after a split. This map can be implicit or explicit.   Although FUs can have multiple input-pins it is preferrable in most cases to combine input data from different branches using an explicit join: The default output of a join is a tuple of its input values. The default behavior of a join is to output a value whenever a new input is received. However, to produce its first output a join needs an input for all its input-pins. Other join behaviors can be: reset all inputs after an output only produce output if data arrives on certain input-pins

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• byte and short data types in Java can accept the value outside the range by explicit cast. The higher data types however can not. Why?

  - by Lion

  Let's consider the following expressions in Java. byte a = 32; byte b = (byte) 250; int i = a + b; This is valid in Java even though the expression byte b = (byte) 250; is forced to assign the value 250 to b which is outside the range of the type byte. Therefore, b is assigned -6 and consequently i is assigned the value 26 through the statement int i = a + b;. The same thing is possible with short as follows. short s1=(short) 567889999; Although the specified value is outside the range of short, this statement is legal. The same thing is however wrong with higher data types such int, double, folat etc and hence, the following case is invalid and causes a compile-time error. int z=2147483648; This is illegal, since the range of int in Java is from -2,147,483,648 to 2147483647 which the above statement exceeds and issues a compile-time error. Why is such not wrong with byte and short data types in Java?

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• Checking preconditions or not

  - by Robert Dailey

  I've been wanting to find a solid answer to the question of whether or not to have runtime checks to validate input for the purposes of ensuring a client has stuck to their end of the agreement in design by contract. For example, consider a simple class constructor: class Foo { public: Foo( BarHandle bar ) { FooHandle handle = GetFooHandle( bar ); if( handle == NULL ) { throw std::exception( "invalid FooHandle" ); } } }; I would argue in this case that a user should not attempt to construct a Foo without a valid BarHandle. It doesn't seem right to verify that bar is valid inside of Foo's constructor. If I simply document that Foo's constructor requires a valid BarHandle, isn't that enough? Is this a proper way to enforce my precondition in design by contract? So far, everything I've read has mixed opinions on this. It seems like 50% of people would say to verify that bar is valid, the other 50% would say that I shouldn't do it, for example consider a case where the user verifies their BarHandle is correct, but a second (and unnecessary) check is also being done inside of Foo's constructor.

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• F# Objects &ndash; Part 3 &ndash; it&rsquo;s time to overload&hellip;

  - by MarkPearl

  Okay, some basic examples of overloading in F# Overloading Constructors Assume you have a F# object called person… type Person (firstname : string, lastname : string) = member v.Fullname = firstname + " " + lastname   This only has one constructor. To add additional constructors to the object by explicitly declaring them using the method member new. type Person (firstname : string, lastname : string) = new () = Person("Unknown", "Unknown") member v.Fullname = firstname + " " + lastname   In the code above I added another constructor to the Person object that takes no parameters and then refers to the primary constructor. Using the same technique in the code below I have created another constructor that accepts only the firstname as a parameter to create an object. type Person (firstname : string, lastname : string) = new () = Person("Unknown", "Unknown") new (firstname : string) = Person(firstname, "Unknown") member v.Fullname = firstname + " " + lastname   Overloading Operators So, you can overload operators of objects in F# as well… let’s look at example code… type Person(name : string) = member v.name = name static member (+) (person1 : Person , person2 : Person) = Person(person1.name + " " + person2.name)   In the code above we have overloaded the “+” operator. Whenever we add to Person objects together, it will now create a new object with the combined names…

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• How-to configure Spring Social via XML

  - by Matthias Steiner

  I spend a few hours trying to get Twitter integration to work with Spring Social using the XML configuration approach. All the examples I could find on the web (and on stackoverflow) always use the @Config approach as shown in the samples For whatever reason the bean definition to get an instance to the twitter API throws an AOP exception: Caused by: java.lang.IllegalStateException: Cannot create scoped proxy for bean 'scopedTarget.twitter': Target type could not be determined at the time of proxy creation. Here's the complete config file I have: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jaxrs="http://cxf.apache.org/jaxrs" xmlns:context="http://www.springframework.org/schema/context" xmlns:util="http://www.springframework.org/schema/util" xmlns:cxf="http://cxf.apache.org/core" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:jee="http://www.springframework.org/schema/jee" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd http://cxf.apache.org/core http://cxf.apache.org/schemas/core.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.1.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.1.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd"> <import resource="classpath:META-INF/cxf/cxf.xml" /> <import resource="classpath:META-INF/cxf/cxf-servlet.xml" /> <jee:jndi-lookup id="dataSource" jndi-name="java:comp/env/jdbc/DefaultDB" /> <!-- initialize DB required to store user auth tokens --> <jdbc:initialize-database data-source="dataSource" ignore-failures="ALL"> <jdbc:script location="classpath:/org/springframework/social/connect/jdbc/JdbcUsersConnectionRepository.sql"/> </jdbc:initialize-database> <bean id="connectionFactoryLocator" class="org.springframework.social.connect.support.ConnectionFactoryRegistry"> <property name="connectionFactories"> <list> <ref bean="twitterConnectFactory" /> </list> </property> </bean> <bean id="twitterConnectFactory" class="org.springframework.social.twitter.connect.TwitterConnectionFactory"> <constructor-arg value="xyz" /> <constructor-arg value="xzy" /> </bean> <bean id="usersConnectionRepository" class="org.springframework.social.connect.jdbc.JdbcUsersConnectionRepository"> <constructor-arg ref="dataSource" /> <constructor-arg ref="connectionFactoryLocator" /> <constructor-arg ref="textEncryptor" /> </bean> <bean id="connectionRepository" factory-method="createConnectionRepository" factory-bean="usersConnectionRepository" scope="request"> <constructor-arg value="#{request.userPrincipal.name}" /> <aop:scoped-proxy proxy-target-class="false" /> </bean> <bean id="twitter" factory-method="?ndPrimaryConnection" factory-bean="connectionRepository" scope="request" depends-on="connectionRepository"> <constructor-arg value="org.springframework.social.twitter.api.Twitter" /> <aop:scoped-proxy proxy-target-class="false" /> </bean> <bean id="textEncryptor" class="org.springframework.security.crypto.encrypt.Encryptors" factory-method="noOpText" /> <bean id="connectController" class="org.springframework.social.connect.web.ConnectController"> <constructor-arg ref="connectionFactoryLocator"/> <constructor-arg ref="connectionRepository"/> <property name="applicationUrl" value="https://socialscn.int.netweaver.ondemand.com/socialspringdemo" /> </bean> <bean id="signInAdapter" class="com.sap.netweaver.cloud.demo.social.SimpleSignInAdapter" /> </beans> What puzzles me is that the connectionRepositoryinstantiation works perfectly fine (I commented-out the twitter bean and tested the code!) ?!? It uses the same features: request scope and interface AOP proxy and works, but the twitter bean instantiation fails ?!? The spring social config code looks as follows (I can not see any differences, can you?): @Configuration public class SocialConfig { @Inject private Environment environment; @Inject private DataSource dataSource; @Bean @Scope(value="singleton", proxyMode=ScopedProxyMode.INTERFACES) public ConnectionFactoryLocator connectionFactoryLocator() { ConnectionFactoryRegistry registry = new ConnectionFactoryRegistry(); registry.addConnectionFactory(new TwitterConnectionFactory(environment.getProperty("twitter.consumerKey"), environment.getProperty("twitter.consumerSecret"))); return registry; } @Bean @Scope(value="singleton", proxyMode=ScopedProxyMode.INTERFACES) public UsersConnectionRepository usersConnectionRepository() { return new JdbcUsersConnectionRepository(dataSource, connectionFactoryLocator(), Encryptors.noOpText()); } @Bean @Scope(value="request", proxyMode=ScopedProxyMode.INTERFACES) public ConnectionRepository connectionRepository() { Authentication authentication = SecurityContextHolder.getContext().getAuthentication(); if (authentication == null) { throw new IllegalStateException("Unable to get a ConnectionRepository: no user signed in"); } return usersConnectionRepository().createConnectionRepository(authentication.getName()); } @Bean @Scope(value="request", proxyMode=ScopedProxyMode.INTERFACES) public Twitter twitter() { Connection<Twitter> twitter = connectionRepository().findPrimaryConnection(Twitter.class); return twitter != null ? twitter.getApi() : new TwitterTemplate(); } @Bean public ConnectController connectController() { ConnectController connectController = new ConnectController(connectionFactoryLocator(), connectionRepository()); connectController.addInterceptor(new PostToWallAfterConnectInterceptor()); connectController.addInterceptor(new TweetAfterConnectInterceptor()); return connectController; } @Bean public ProviderSignInController providerSignInController(RequestCache requestCache) { return new ProviderSignInController(connectionFactoryLocator(), usersConnectionRepository(), new SimpleSignInAdapter(requestCache)); } } Any help/pointers would be appreciated!!! Cheers, Matthias

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• Using Unity – Part 5

  - by nmarun

  In the previous article of the series, I talked about constructor and property (setter) injection. I wanted to write about how to work with arrays and generics in Unity in this blog, after seeing how lengthy this one got, I’ve decided to write about generics in the next one. This one will only concentrate on arrays. My Product4 class has the following definition: 1: public interface IProduct 2: { 3: string WriteProductDetails(); 4: } 5:  6: public class Product4 : IProduct 7: { 8: public string Name { get; set; } 9: public ILogger[] Loggers { get; set; } 10:  11: public Product4(string productName, ILogger[] loggers) 12: { 13: Name = productName; 14: Loggers = loggers; 15: } 16:  17: public string WriteProductDetails() 18: { 19: StringBuilder productDetails = new StringBuilder(); 20: productDetails.AppendFormat("{0}<br/>", Name); 21: for (int i = 0; i < Loggers.Count(); i++) 22: { 23: productDetails.AppendFormat("{0}<br/>", Loggers[i].WriteLog()); 24: } 25: 26: return productDetails.ToString(); 27: } 28: } The key parts are line 4 where we declare an array of ILogger and line 5 where-in the constructor passes an instance of an array of ILogger objects. I’ve created another class – FakeLogger: 1: public class FakeLogger : ILogger 2: { 3: public string WriteLog() 4: { 5: return string.Format("Type: {0}", GetType()); 6: } 7: } It’s implementation is the same as what we had for the FileLogger class. Coming to the web.config file, first add the following aliases. The alias for FakeLogger should make sense right away. ILoggerArray defines an array of ILogger objects. I’ll tell why we need an alias for System.String data type. 1: <typeAlias alias="string" type="System.String, mscorlib" /> 2: <typeAlias alias="ILoggerArray" type="ProductModel.ILogger[], ProductModel" /> 3: <typeAlias alias="FakeLogger" type="ProductModel.FakeLogger, ProductModel"/> Next is to create mappings for the FileLogger and FakeLogger classes: 1: <type type="ILogger" mapTo="FileLogger" name="logger1"> 2: <lifetime type="singleton" /> 3: </type> 4: <type type="ILogger" mapTo="FakeLogger" name="logger2"> 5: <lifetime type="singleton" /> 6: </type> Finally, for the real deal: 1: <type type="IProduct" mapTo="Product4" name="ArrayProduct"> 2: <typeConfig extensionType="Microsoft.Practices.Unity.Configuration.TypeInjectionElement,Microsoft.Practices.Unity.Configuration, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"> 3: <constructor> 4: <param name="productName" parameterType="string" > 5: <value value="Product name from config file" type="string"/> 6: </param> 7: <param name="loggers" parameterType="ILoggerArray"> 8: <array> 9: <dependency name="logger2" /> 10: <dependency name="logger1" /> 11: </array> 12: </param> 13: </constructor> 14: </typeConfig> 15: </type> Here’s where I’m saying, that if a type of IProduct is requested to be resolved, map it to type Product4. Furthermore, the Product4 has two constructor parameters – a string and an array of type ILogger. You might have observed the first parameter of the constructor is named ‘productName’ and that matches the value in the name attribute of the param element. The parameterType of ‘string’ maps to ‘System.String, mscorlib’ and is defined in the type alias above. The set up is similar for the second constructor parameter. The name matches the name of the parameter (loggers) and is of type ILoggerArray, which maps to an array of ILogger objects. We’ve also decided to add two elements to this array when unity resolves it – an instance of FileLogger and one of FakeLogger. The click event of the button does the following: 1: //unityContainer.RegisterType<IProduct, Product4>(); 2: //IProduct product4 = unityContainer.Resolve<IProduct>(); 3: IProduct product4 = unityContainer.Resolve<IProduct>("ArrayConstructor"); 4: productDetailsLabel.Text = product4.WriteProductDetails(); It’s worth mentioning here about the change in the format of resolving the IProduct to create an instance of Product4. You cannot use the regular way (the commented lines) to get an instance of Product4. The reason is due to the behavior of Unity which Alex Ermakov has brilliantly explained here. The corresponding output of the action is: You have a couple of options when it comes to adding dependency elements in the array node. You can: - leave it empty (no dependency elements declared): This will only create an empty array of loggers. This way you can check for non-null condition, in your mock classes. - add multiple dependency elements with the same name 1: <param name="loggers" parameterType="ILoggerArray"> 2: <array> 3: <dependency name="logger2" /> 4: <dependency name="logger2" /> 5: </array> 6: </param> With this you’ll see two instances of FakeLogger in the output. This article shows how Unity allows you to instantiate objects with arrays. Find the code here.

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• ASP.NET exception gives irrelevant stack trace on YSOD, very challenging!

  - by pootow

  Here is the YSOD: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.] System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +428 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 ECommerce.PMethod.Sql.SqlConns.Open() +78 ECommerce.PMethod.Sql.SqlConns..ctor() +120 ECommerce.login.DatasInfo.Proc.UserCenter.IsLogin(String UserGUID, Int32 UserID) +49 ECommerce.login.Rules.Users.UserLogin.isLogin() +44 Config.isUserLogined() +5 Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +99 System.Web.UI.Control.LoadRecursive() +50 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627 [TypeInitializationException: The type initializer for 'ECommerce.ERP.DAL.DBConn' threw an exception.] ECommerce.ERP.DAL.DBConn.get_ConnString() +0 [ObjectDefinitionStoreException: Factory method 'System.String get_ConnString()' threw an Exception.] Spring.Objects.Factory.Support.SimpleInstantiationStrategy.Instantiate(RootObjectDefinition definition, String name, IObjectFactory factory, MethodInfo factoryMethod, Object[] arguments) +257 Spring.Objects.Factory.Support.ConstructorResolver.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +624 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +60 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +56 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +436 [ObjectCreationException: Error thrown by a dependency of object 'styleService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 56' : Initialization of object failed : Factory method 'System.String get_ConnString()' threw an Exception. while resolving 'constructor argument with name promotionservice' to 'promotionService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 31' while resolving 'constructor argument with name domainservice' to 'promotionDomainService' defined in 'assembly [ECommerce.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Domain.AppContext.xml] line 20' while resolving 'constructor argument with name promotionrepos' to 'promotionRepos' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34' while resolving 'constructor argument with name connstr' to 'ECommerce.ERP.DAL.DBConn#389F399' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34'] Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveReference(IObjectDefinition definition, String name, String argumentName, RuntimeObjectReference reference) +394 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolvePropertyValue(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +312 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveValueIfNecessary(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +17 Spring.Objects.Factory.Support.ConstructorResolver.ResolveConstructorArguments(String objectName, RootObjectDefinition definition, ObjectWrapper wrapper, ConstructorArgumentValues cargs, ConstructorArgumentValues resolvedValues) +993 Spring.Objects.Factory.Support.ConstructorResolver.AutowireConstructor(String objectName, RootObjectDefinition rod, ConstructorInfo[] chosenCtors, Object[] explicitArgs) +171 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.AutowireConstructor(String name, RootObjectDefinition definition, ConstructorInfo[] ctors, Object[] explicitArgs) +65 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +161 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +636 Spring.Objects.Factory.Support.AbstractObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +174 Spring.Objects.Factory.Support.WebObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +150 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObjectInternal(String name, Type requiredType, Object[] arguments, Boolean suppressConfigure) +990 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObject(String name) +10 Spring.Context.Support.AbstractApplicationContext.GetObject(String name) +20 ECommerce.Common.ServiceLocator.GetService() +334 ECommerce.Mvc.Controllers.StylesController..ctor() +72 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) +86 System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) +230 System.Activator.CreateInstance(Type type, Boolean nonPublic) +67 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +80 [InvalidOperationException: An error occurred when trying to create a controller of type 'ECommerce.Mvc.Controllers.StylesController'. Make sure that the controller has a parameterless public constructor.] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +190 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +68 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +118 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +46 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +63 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +13 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8677954 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082 Question is: the first stack trace is irrelevant to others, what happened? Any ideas? Let me make this more clear: a MVC page uses the spring part trying to load a lazy-init service which constructor wants a connection string through a static property like this: <object id="promotionRepos" type="ECommerce.Data.AdoNet.Promotions.PromotionRepos, ECommerce.Data.AdoNet" lazy-init="true"> <constructor-arg name="provider"> <null /> </constructor-arg> <constructor-arg name="connStr"> <object type="ECommerce.ERP.DAL.DBConn, ECommerce.ERP.DAL" factory-method="get_ConnString" /> </constructor-arg> <property name="RefreshInterval" value="00:00:10" /> </object> the timeout part is some what irrelevent to all others. see this in the first exception: Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 it's another page at all. And also, ECommerce.PMethod.Sql.SqlConns.Open() uses its own connection string, not the one loaded by spring, it's different module from diffrent team. And I am sure the connection string is correct. And, this ysod cames up randomly. Sometimes nothing is wrong, and sometimes, it appears. I thought there could be something wrong with my database or the network/firewall, I will check it later, but now I want understand this tricky stack trace.

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• initctl respawn does not reload configuration

  - by DELUXEnized

  My upstart service is running with the respawn option. I was hoping that if I deploy a new service config, the config will be loaded, when the service respawns. Neither the initctl reload-configuration command forces a reload, nor the restart command. Only an explicit stop and start reloads the configuration. The problem is, that I can not stop and start the service, at deploy time. The service itself schedules its restart by just shutting down. Is this behavior by design or am I missing something? Would it change anything, if I did the respawn with a second watchdog-service by an explicit start if my service stops? Why is there a difference between an explicit start/stop and the restart command or respawn option. Thanks.

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• Why can't we capture the design of software more effectively?

  - by Ira Baxter

  As engineers, we all "design" artifacts (buildings, programs, circuits, molecules...). That's an activity (design-the-verb) that produces some kind of result (design-the-noun). I think we all agree that design-the-noun is a different entity than the artifact itself. A key activity in the software business (indeed, in any business where the resulting product artifact needs to be enhanced) is to understand the "design (the-noun)". Yet we seem, as a community, to be pretty much complete failures at recording it, as evidenced by the amount of effort people put into rediscovering facts about their code base. Ask somebody to show you the design of their code and see what you get. I think of a design for software as having: An explicit specification for what the software is supposed to do and how well it does it An explicit version of the code (this part is easy, everybody has it) An explanation for how each part of the code serves to achieve the specification A rationale as to why the code is the way it is (e.g., why a particualr choice rather than another) What is NOT a design is a particular perspective on the code. For example [not to pick specifically on] UML diagrams are not designs. Rather, they are properties you can derive from the code, or arguably, properties you wish you could derive from the code. But as a general rule, you can't derive the code from UML. Why is it that after 50+ years of building software, why don't we have regular ways to express this? My personal opinion is that we don't have good ways to express this. Even if we do, most of the community seems so focused on getting "code" that design-the-noun gets lost anyway. (IMHO, until design becomes the purpose of engineering, with the artifact extracted from the design, we're not going to get around this). What have you seen as means for recording designs (in the sense I have described it)? Explicit references to papers would be good. Why do you think specific and general means have not been succesful? How can we change this?

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• How can I improve my error checking and handling?

  - by Google

  Lately I have been struggling to understand what the right amount of checking is and what the proper methods are. I have a few questions regarding this: What is the proper way to check for errors (bad input, bad states, etc)? Is it better to explicitly check for errors, or use functions like asserts which can be optimized out of your final code? I feel like explicitly checking clutters a program with a lot of extra code which shouldn't be executed in most situations anyway-- and not to mention most errors end up with an abort/exit failure. Why clutter a function with explicit checks just to abort? I have looked for asserts versus explicit checking of errors and found little to truly explain when to do either. Most say 'use asserts to check for logic errors and use explicit checks to check for other failures.' This doesn't seem to get us very far though. Would we say this is feasible: Malloc returning null, check explictly API user inserting odd input for functions, use asserts Would this make me any better at error checking? What else can I do? I really want to improve and write better, 'professional' code.

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• Yet Yet Another Way To Create An Object

  - by Ricardo Peres

  Yep, there's still another one: FormatterServices. This one allows one to create an object without running it's constructor... it is used by some of our good friends serializers. Stopwatch watch = new Stopwatch(); for (Int32 i = 0; i Beware, though: because the constructor isn't run (and remember that all fields that are initialized inline are also in fact initialized in the constructor), the object's state may be invalid. Enough object construction for now... SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• Please help me to improve Re-Sharper

  - by TATWORTH

  Re-Sharper is an excellent aid to producing good code in either C# or VB.NET. Recently through using Resharper and StyleCop, I have found three area where ReSharper needs to be improved. Please log into the YouTrack at http://youtrack.jetbrains.net and vote for the following: RSRP-268868 Improvement to removal of redundant else and invert if optimisations for enhanced stylecop compliance. When Resharper removes a redundant else, there needs to be a blank line added. Currently there is no provision to specify this. Please vote for this! RSRP-272286 Resharper Feature Request to move initialisation to static constructor Currently ReSharper offers moving initialisation of of non-static variable to a constructor. Why not offer the same for a static constructor?  Please vote for this! RSRP-272285 Expansion of Switch Statement by Resharper Currently ReSharper will fill an empty switch statement based upon an enumeration but will not add missing enumeration values to such a switch statement.   Can't code withoutCoding assistance, smart code editing and code completion for C# and VB.NET

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• C#/.NET Little Pitfalls: The Dangers of Casting Boxed Values

  - by James Michael Hare

  Starting a new series to parallel the Little Wonders series.  In this series, I will examine some of the small pitfalls that can occasionally trip up developers. Introduction: Of Casts and Conversions What happens when we try to assign from an int and a double and vice-versa? 1: double pi = 3.14; 2: int theAnswer = 42; 3:  4: // implicit widening conversion, compiles! 5: double doubleAnswer = theAnswer; 6:  7: // implicit narrowing conversion, compiler error! 8: int intPi = pi; As you can see from the comments above, a conversion from a value type where there is no potential data loss is can be done with an implicit conversion.  However, when converting from one value type to another may result in a loss of data, you must make the conversion explicit so the compiler knows you accept this risk.  That is why the conversion from double to int will not compile with an implicit conversion, we can make the conversion explicit by adding a cast: 1: // explicit narrowing conversion using a cast, compiler 2: // succeeds, but results may have data loss: 3: int intPi = (int)pi; So for value types, the conversions (implicit and explicit) both convert the original value to a new value of the given type.  With widening and narrowing references, however, this is not the case.  Converting reference types is a bit different from converting value types.  First of all when you perform a widening or narrowing you don’t really convert the instance of the object, you just convert the reference itself to the wider or narrower reference type, but both the original and new reference type both refer back to the same object. Secondly, widening and narrowing for reference types refers the going down and up the class hierarchy instead of referring to precision as in value types.  That is, a narrowing conversion for a reference type means you are going down the class hierarchy (for example from Shape to Square) whereas a widening conversion means you are going up the class hierarchy (from Square to Shape).  1: var square = new Square(); 2:  3: // implicitly convers because all squares are shapes 4: // (that is, all subclasses can be referenced by a superclass reference) 5: Shape myShape = square; 6:  7: // implicit conversion not possible, not all shapes are squares! 8: // (that is, not all superclasses can be referenced by a subclass reference) 9: Square mySquare = (Square) myShape; So we had to cast the Shape back to Square because at that point the compiler has no way of knowing until runtime whether the Shape in question is truly a Square.  But, because the compiler knows that it’s possible for a Shape to be a Square, it will compile.  However, if the object referenced by myShape is not truly a Square at runtime, you will get an invalid cast exception. Of course, there are other forms of conversions as well such as user-specified conversions and helper class conversions which are beyond the scope of this post.  The main thing we want to focus on is this seemingly innocuous casting method of widening and narrowing conversions that we come to depend on every day and, in some cases, can bite us if we don’t fully understand what is going on!  The Pitfall: Conversions on Boxed Value Types Can Fail What if you saw the following code and – knowing nothing else – you were asked if it was legal or not, what would you think: 1: // assuming x is defined above this and this 2: // assignment is syntactically legal. 3: x = 3.14; 4:  5: // convert 3.14 to int. 6: int truncated = (int)x; You may think that since x is obviously a double (can’t be a float) because 3.14 is a double literal, but this is inaccurate.  Our x could also be dynamic and this would work as well, or there could be user-defined conversions in play.  But there is another, even simpler option that can often bite us: what if x is object? 1: object x; 2:  3: x = 3.14; 4:  5: int truncated = (int) x; On the surface, this seems fine.  We have a double and we place it into an object which can be done implicitly through boxing (no cast) because all types inherit from object.  Then we cast it to int.  This theoretically should be possible because we know we can explicitly convert a double to an int through a conversion process which involves truncation. But here’s the pitfall: when casting an object to another type, we are casting a reference type, not a value type!  This means that it will attempt to see at runtime if the value boxed and referred to by x is of type int or derived from type int.  Since it obviously isn’t (it’s a double after all) we get an invalid cast exception! Now, you may say this looks awfully contrived, but in truth we can run into this a lot if we’re not careful.  Consider using an IDataReader to read from a database, and then attempting to select a result row of a particular column type: 1: using (var connection = new SqlConnection("some connection string")) 2: using (var command = new SqlCommand("select * from employee", connection)) 3: using (var reader = command.ExecuteReader()) 4: { 5: while (reader.Read()) 6: { 7: // if the salary is not an int32 in the SQL database, this is an error! 8: // doesn't matter if short, long, double, float, reader [] returns object! 9: total += (int) reader["annual_salary"]; 10: } 11: } Notice that since the reader indexer returns object, if we attempt to convert using a cast to a type, we have to make darn sure we use the true, actual type or this will fail!  If the SQL database column is a double, float, short, etc this will fail at runtime with an invalid cast exception because it attempts to convert the object reference! So, how do you get around this?  There are two ways, you could first cast the object to its actual type (double), and then do a narrowing cast to on the value to int.  Or you could use a helper class like Convert which analyzes the actual run-time type and will perform a conversion as long as the type implements IConvertible. 1: object x; 2:  3: x = 3.14; 4:  5: // if you want to cast, must cast out of object to double, then 6: // cast convert. 7: int truncated = (int)(double) x; 8:  9: // or you can call a helper class like Convert which examines runtime 10: // type of the value being converted 11: int anotherTruncated = Convert.ToInt32(x); Summary You should always be careful when performing a conversion cast from values boxed in object that you are actually casting to the true type (or a sub-type). Since casting from object is a widening of the reference, be careful that you either know the exact, explicit type you expect to be held in the object, or instead avoid the cast and use a helper class to perform a safe conversion to the type you desire. Technorati Tags: C#,.NET,Pitfalls,Little Pitfalls,BlackRabbitCoder

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• Creating Entity Framework objects with Unity for Unit of Work/Repository pattern

  - by TobyEvans

  Hi there, I'm trying to implement the Unit of Work/Repository pattern, as described here: http://blogs.msdn.com/adonet/archive/2009/06/16/using-repository-and-unit-of-work-patterns-with-entity-framework-4-0.aspx This requires each Repository to accept an IUnitOfWork implementation, eg an EF datacontext extended with a partial class to add an IUnitOfWork interface. I'm actually using .net 3.5, not 4.0. My basic Data Access constructor looks like this: public DataAccessLayer(IUnitOfWork unitOfWork, IRealtimeRepository realTimeRepository) { this.unitOfWork = unitOfWork; this.realTimeRepository = realTimeRepository; } So far, so good. What I'm trying to do is add Dependency Injection using the Unity Framework. Getting the EF data context to be created with Unity was an adventure, as it had trouble resolving the constructor - what I did in the end was to create another constructor in my partial class with a new overloaded constructor, and marked that with [InjectionConstructor] [InjectionConstructor] public communergyEntities(string connectionString, string containerName) :this() { (I know I need to pass the connection string to the base object, that can wait until once I've got all the objects initialising correctly) So, using this technique, I can happily resolve my entity framework object as an IUnitOfWork instance thus: using (IUnityContainer container = new UnityContainer()) { container.RegisterType<IUnitOfWork, communergyEntities>(); container.Configure<InjectedMembers>() .ConfigureInjectionFor<communergyEntities>( new InjectionConstructor("a", "b")) DataAccessLayer target = container.Resolve<DataAccessLayer>(); Great. What I need to do now is create the reference to the repository object for the DataAccessLayer - the DAL only needs to know the interface, so I'm guessing that I need to instantiate it as part of the Unity Resolve statement, passing it the appropriate IUnitOfWork interface. In the past, I would have just passed the Repository constructor the db connection string, and it would have gone away, created a local Entity Framework object and used that just for the lifetime of the Repository method. This is different, in that I create an Entity Framework instance as an IUnitOfWork implementation during the Unity Resolve statement, and it's that instance I need to pass into the constructor of the Repository - is that possible, and if so, how? I'm wondering if I could make the Repository a property and mark it as a Dependency, but that still wouldn't solve the problem of how to create the Repository with the IUnitOfWork object that the DAL is being Resolved with I'm not sure if I've understood this pattern correctly, and will happily take advice on the best way to implement it - Entity Framework is staying, but Unity can be swapped out if not the best approach. If I've got the whole thing upside down, please tell me thanks

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• How to send keypresses from qt application to libvlc

  - by anon

  I need to send keypresses from my application window to libvlc, how do i do that? I tried using varSetInteger but then i got the following error error: ‘var_SetInteger’ was not declared in this scope so i searched for the file in which var_SetInteger was defined and found that it was defined in vlc_variables.h so in included it and got the following error. What am i missing? ../vlc-0.9.10/include/vlc_variables.h:121: error: ‘__var_Create’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:121: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:121: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:121: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:121: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:122: error: ‘__var_Destroy’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:122: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:122: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:122: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:122: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:124: error: ‘__var_Change’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:124: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:124: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:124: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:124: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:126: error: ‘__var_Type’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:126: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:126: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:126: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:126: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:127: error: ‘__var_Set’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:127: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:127: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:127: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:127: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:128: error: ‘__var_Get’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:128: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:128: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:128: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:128: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:131: error: ‘__var_Command’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:131: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:131: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:131: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:131: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:133: error: expected constructor, destructor, or type conversion before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:171: error: ‘__var_AddCallback’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:171: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:171: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:171: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:171: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:172: error: ‘__var_DelCallback’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:172: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:172: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:172: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:172: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:173: error: ‘__var_TriggerCallback’ has not been declared ../vlc-0.9.10/include/vlc_variables.h:173: error: expected identifier before ‘(’ token ../vlc-0.9.10/include/vlc_variables.h:173: error: expected )' before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:173: error: expected ‘,’ or ‘...’ before ‘*’ token ../vlc-0.9.10/include/vlc_variables.h:173: error: expected constructor, destructor, or type conversion before ‘)’ token ../vlc-0.9.10/include/vlc_variables.h:201: error: ‘__var_SetInteger’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:201: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:201: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:201: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:201: error: expected primary-expression before ‘int’ ../vlc-0.9.10/include/vlc_variables.h:201: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:202: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:215: error: ‘__var_SetBool’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:215: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:215: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:215: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:215: error: expected primary-expression before ‘bool’ ../vlc-0.9.10/include/vlc_variables.h:215: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:216: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:229: error: ‘__var_SetTime’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:229: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:229: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:229: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:229: error: expected primary-expression before ‘i’ ../vlc-0.9.10/include/vlc_variables.h:229: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:230: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:243: error: ‘__var_SetFloat’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:243: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:243: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:243: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:243: error: expected primary-expression before ‘float’ ../vlc-0.9.10/include/vlc_variables.h:243: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:244: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:257: error: ‘__var_SetString’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:257: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:257: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:257: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:257: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:257: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:258: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:270: error: ‘__var_SetVoid’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:270: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:270: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:270: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:270: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:271: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:302: error: ‘__var_GetInteger’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:302: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:302: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:302: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:302: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:303: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:317: error: ‘__var_GetBool’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:317: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:317: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:317: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:317: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:318: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:332: error: ‘__var_GetTime’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:332: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:332: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:332: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:332: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:333: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:347: error: ‘__var_GetFloat’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:347: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:347: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:347: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:347: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:348: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:362: error: ‘__var_GetString’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:362: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:362: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:362: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:362: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:363: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:371: error: ‘__var_GetNonEmptyString’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:371: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:371: error: ‘obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:371: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:371: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:372: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:412: error: variable or field ‘__var_IncInteger’ declared void ../vlc-0.9.10/include/vlc_variables.h:412: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:412: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:412: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:424: error: variable or field ‘__var_DecInteger’ declared void ../vlc-0.9.10/include/vlc_variables.h:424: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:424: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:424: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:437: error: ‘__var_CreateGetInteger’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:437: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:437: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:437: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:437: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:438: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:449: error: ‘__var_CreateGetBool’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:449: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:449: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:449: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:449: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:450: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:461: error: ‘__var_CreateGetTime’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:461: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:461: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:461: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:461: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:462: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:473: error: ‘__var_CreateGetFloat’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:473: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:473: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:473: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:473: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:474: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:485: error: ‘__var_CreateGetString’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:485: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:485: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:486: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:486: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:487: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:492: error: ‘__var_CreateGetNonEmptyString’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:492: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:492: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:493: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:493: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:494: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:527: error: ‘__var_CreateGetIntegerCommand’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:527: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:527: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:527: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:527: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:528: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:540: error: ‘__var_CreateGetBoolCommand’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:540: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:540: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:540: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:540: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:541: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:553: error: ‘__var_CreateGetTimeCommand’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:553: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:553: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:553: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:553: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:554: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:566: error: ‘__var_CreateGetFloatCommand’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:566: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:566: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:566: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:566: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:567: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:579: error: ‘__var_CreateGetStringCommand’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:579: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:579: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:580: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:580: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:581: error: expected ‘,’ or ‘;’ before ‘{’ token ../vlc-0.9.10/include/vlc_variables.h:587: error: ‘__var_CreateGetNonEmptyStringCommand’ declared as an ‘inline’ variable ../vlc-0.9.10/include/vlc_variables.h:587: error: ‘vlc_object_t’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:587: error: ‘p_obj’ was not declared in this scope ../vlc-0.9.10/include/vlc_variables.h:588: error: expected primary-expression before ‘const’ ../vlc-0.9.10/include/vlc_variables.h:588: error: initializer expression list treated as compound expression ../vlc-0.9.10/include/vlc_variables.h:589: error: expected ‘,’ or ‘;’ before ‘{’ token src/transcribeWidget.cpp:859: warning: unused parameter ‘bytesSent’ src/transcribeWidget.cpp:859: warning: unused parameter ‘bytesTotal’ ../vlc-0.9.10/include/vlc_variables.h:201: warning: ‘__var_SetInteger’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:215: warning: ‘__var_SetBool’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:229: warning: ‘__var_SetTime’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:243: warning: ‘__var_SetFloat’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:257: warning: ‘__var_SetString’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:270: warning: ‘__var_SetVoid’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:302: warning: ‘__var_GetInteger’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:317: warning: ‘__var_GetBool’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:332: warning: ‘__var_GetTime’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:347: warning: ‘__var_GetFloat’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:362: warning: ‘__var_GetString’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:371: warning: ‘__var_GetNonEmptyString’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:437: warning: ‘__var_CreateGetInteger’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:449: warning: ‘__var_CreateGetBool’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:461: warning: ‘__var_CreateGetTime’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:473: warning: ‘__var_CreateGetFloat’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:485: warning: ‘__var_CreateGetString’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:492: warning: ‘__var_CreateGetNonEmptyString’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:527: warning: ‘__var_CreateGetIntegerCommand’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:540: warning: ‘__var_CreateGetBoolCommand’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:553: warning: ‘__var_CreateGetTimeCommand’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:566: warning: ‘__var_CreateGetFloatCommand’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:579: warning: ‘__var_CreateGetStringCommand’ defined but not used ../vlc-0.9.10/include/vlc_variables.h:587: warning: ‘__var_CreateGetNonEmptyStringCommand’ defined but not used

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• Rhino Mocks, Dependency Injection, and Separation of Concerns

  - by whatispunk

  I am new to mocking and dependency injection and need some guidance. My application is using a typical N-Tier architecture where the BLL references the DAL, and the UI references the BLL but not the DAL. Pretty straight forward. Lets say, for example, I have the following classes: class MyDataAccess : IMyDataAccess {} class MyBusinessLogic {} Each exists in a separate assembly. I want to mock MyDataAccess in the tests for MyBusinessLogic. So I added a constructor to the MyBusinessLogic class to take an IMyDataAccess parameter for the dependency injection. But now when I try to create an instance of MyBusinessLogic on the UI layer it requires a reference to the DAL. I thought I could define a default constructor on MyBusinessLogic to set a default IMyDataAccess implementation, but not only does this seem like a codesmell it didn't actually solve the problem. I'd still have a public constructor with IMyDataAccess in the signature. So the UI layer still requires a reference to the DAL in order to compile. One possible solution I am toying with is to create an internal constructor for MyBusinessLogic with the IMyDataAccess parameter. Then I can use an Accessor from the test project to call the constructor. But there's still that smell. What is the common solution here. I must just be doing something wrong. How could I improve the architecture?

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• DynamicMethod for ConstructorInfo.Invoke, what do I need to consider?

  - by Lasse V. Karlsen

  My question is this: If I'm going to build a DynamicMethod object, corresponding to a ConstructorInfo.Invoke call, what types of IL do I need to implement in order to cope with all (or most) types of arguments, when I can guarantee that the right type and number of arguments is going to be passed in before I make the call? Background I am on my 3rd iteration of my IoC container, and currently doing some profiling to figure out if there are any areas where I can easily shave off large amounts of time being used. One thing I noticed is that when resolving to a concrete type, ultimately I end up with a constructor being called, using ConstructorInfo.Invoke, passing in an array of arguments that I've worked out. What I noticed is that the invoke method has quite a bit of overhead, and I'm wondering if most of this is just different implementations of the same checks I do. For instance, due to the constructor matching code I have, to find a matching constructor for the predefined parameter names, types, and values that I have passed in, there's no way this particular invoke call will not end up with something it should be able to cope with, like the correct number of arguments, in the right order, of the right type, and with appropriate values. When doing a profiling session containing a million calls to my resolve method, and then replacing it with a DynamicMethod implementation that mimics the Invoke call, the profiling timings was like this: ConstructorInfo.Invoke: 1973ms DynamicMethod: 93ms This accounts for around 20% of the total runtime of this profiling application. In other words, by replacing the ConstructorInfo.Invoke call with a DynamicMethod that does the same, I am able to shave off 20% runtime when dealing with basic factory-scoped services (ie. all resolution calls end up with a constructor call). I think this is fairly substantial, and warrants a closer look at how much work it would be to build a stable DynamicMethod generator for constructors in this context. So, the dynamic method would take in an object array, and return the constructed object, and I already know the ConstructorInfo object in question. Therefore, it looks like the dynamic method would be made up of the following IL: l001: ldarg.0 ; the object array containing the arguments l002: ldc.i4.0 ; the index of the first argument l003: ldelem.ref ; get the value of the first argument l004: castclass T ; cast to the right type of argument (only if not "Object") (repeat l001-l004 for all parameters, l004 only for non-Object types, varying l002 constant from 0 and up for each index) l005: newobj ci ; call the constructor l006: ret Is there anything else I need to consider? Note that I'm aware that creating dynamic methods will probably not be available when running the application in "reduced access mode" (sometimes the brain just won't give up those terms), but in that case I can easily detect that and just calling the original constructor as before, with the overhead and all.

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• Delegates in .NET: how are they constructed ?

  - by Saulius

  While inspecting delegates in C# and .NET in general, I noticed some interesting facts: Creating a delegate in C# creates a class derived from MulticastDelegate with a constructor: .method public hidebysig specialname rtspecialname instance void .ctor(object 'object', native int 'method') runtime managed { } Meaning that it expects the instance and a pointer to the method. Yet the syntax of constructing a delegate in C# suggests that it has a constructor new MyDelegate(int () target) where I can recognise int () as a function instance (int *target() would be a function pointer in C++). So obviously the C# compiler picks out the correct method from the method group defined by the function name and constructs the delegate. So the first question would be, where does the C# compiler (or Visual Studio, to be precise) pick this constructor signature from ? I did not notice any special attributes or something that would make a distinction. Is this some sort of compiler/visualstudio magic ? If not, is the T (args) target construction valid in C# ? I did not manage to get anything with it to compile, e.g.: int () target = MyMethod; is invalid, so is doing anything with MyMetod, e.g. calling .ToString() on it (well this does make some sense, since that is technically a method group, but I imagine it should be possible to explicitly pick out a method by casting, e.g. (int())MyFunction. So is all of this purely compiler magic ? Looking at the construction through reflector reveals yet another syntax: Func CS$1$0000 = new Func(null, (IntPtr) Foo); This is consistent with the disassembled constructor signature, yet this does not compile! One final interesting note is that the classes Delegate and MulticastDelegate have yet another sets of constructors: .method family hidebysig specialname rtspecialname instance void .ctor(class System.Type target, string 'method') cil managed Where does the transition from an instance and method pointer to a type and a string method name occur ? Can this be explained by the runtime managed keywords in the custom delegate constructor signature, i.e. does the runtime do it's job here ?

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