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• How do I programmatically run all the JUnit tests in my Java application?

  - by Andrew McKinlay

  From Eclipse I can easily run all the JUnit tests in my application. I would like to be able to run the tests on target systems from the application jar, without Eclipse (or Ant or Maven or any other development tool). I can see how to run a specific test or suite from the command line. I could manually create a suite listing all the tests in my application, but that seems error prone - I'm sure at some point I'll create a test and forget to add it to the suite. The Eclipse JUnit plugin has a wizard to create a test suite, but for some reason it doesn't "see" my test classes. It may be looking for JUnit 3 tests, not JUnit 4 annotated tests. I could write a tool that would automatically create the suite by scanning the source files. Or I could write code so the application would scan it's own jar file for tests (either by naming convention or by looking for the @Test annotation). It seems like there should be an easier way. What am I missing?

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• Displaying a collection of objects in a .Net grid on a smartphone without data binding.

  - by Xav

  I know there's No DataGridView in the CF, but I've got a collection of in-memory objects that I want to display in a grid on a phone. Options I have thought of: Stick all the objects into a SQL-CE database and use a bound datagrid. This'll mean pulling my classes apart and separating the data from the functionality, which may or may not be a bad thing, but seems a little overkill. Write my own dataset and binding code so that I can bind my collection of objects to a bound datagrid. No idea how practical or possible this is, but seems like it's either do-able or impossible and I'm hoping someone here knows which! Find a third-party unbound grid control. The only one I've seen mentioned is OpenNetCF, which I'm downloading as I type. Are there others? Are any of them any good? Do something very nasty with dynamically loading labels and textboxes into a scrolling region on the form. REALLY don't want to go there. I'm not much experienced with data-bound controls other than occasionally making use of the very vanilla functionality in WinForms or ASP.Net, and that quite a long time ago, so if any of the above are silly, please be gentle. Thanks Xav

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• Hibernate NamingStrategy implementation that maintains state between calls

  - by Robert Petermeier

  Hi, I'm working on a project where we use Hibernate and JBoss 5.1. We need our entity classes to be mapped to Oracle tables that follow a certain naming convention. I'd like to avoid having to specify each table and column name in annotations. Therefore, I'm currently considering implementing a custom implementation of org.hibernate.cfg.NamingStrategy. The SQL naming conventions require the name of columns to have a suffix that is equivalent to a prefix of the table name. If there is a table "T100_RESOURCE", the ID column would have to be named "RES_ID_T100". In order to implement this in a NamingStrategy, the implementation would have to maintain state, i.e. the current class name it is creating the mappings for. It would rely on Hibernate to always call classToTableName() before propertyToColumnName() and to determine all column names by calling propertyToColumnName() before the next call to classToTableName() Is it safe to do that or are there situations where Hibernate will mix things up? I am not thinking of problems through multiple threads here (which can be solved by keeping the last class name in a ThreadLocal) but also of Hibernate deliberately calling this out of order in certain circumstances. For example Hibernate asking for mappings of three properties of class A, then one of class B, then again more attributes of class A.

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• Is it OK to write code after [super dealloc]? (Objective-C)

  - by Richard J. Ross III

  I have a situation in my code, where I cannot clean up my classes objects without first calling [super dealloc]. It is something like this: // Baseclass.m @implmentation Baseclass ... -(void) dealloc { [self _removeAllData]; [aVariableThatBelongsToMe release]; [anotherVariableThatBelongsToMe release]; [super dealloc]; } ... @end This works great. My problem is, when I went to subclass this huge and nasty class (over 2000 lines of gross code), I ran into a problem: when I released my objects before calling [super dealloc] I had zombies running through the code that were activated when I called the [self _removeAllData] method. // Subclass.m @implementation Subclass ... -(void) deallloc { [super dealloc]; [someObjectUsedInTheRemoveAllDataMethod release]; } ... @end This works great, and It didn't require me to refactor any code. My question Is this: Is it safe for me to do this, or should I refactor my code? Or maybe autorelease the objects? I am programming for iPhone if that matters any.

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• overloading "<<" with a struct (no class) cout style

  - by monkeyking

  I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible without using classes? Thanks #include <iostream> #include <fstream> template <typename T> struct point{ T x; T y; }; template <typename T> std::ostream& dump(std::ostream &o,point<T> p) const{ o<<"x: " << p.x <<"\ty: " << p.y <<std::endl; } template<typename T> std::ostream& operator << (std::ostream &o,const point<T> &a){ return dump(o,a); } int main(){ point<double> p; p.x=0.1; p.y=0.3; dump(std::cout,p); std::cout << p ;//how? return 0; } I tried different syntax' but I cant seem to make it work.

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• Android: How to periodically send location to a server

  - by Mark

  Hi, I am running a Web service that allows users to record their trips (kind of like Google's MyTracks) as part of a larger app. The thing is that it is easy to pass data, including coords and other items, to the server when a user starts a trip or ends it. Being a newbie, I am not sure how to set up a background service that sends the location updates once every (pre-determined) period (min 3 minutes, max 1 hr) until the user flags the end of the trip, or until a preset amount of time elapses. Once the trip is started from the phone, the server responds with a polling period for the phone to use as the interval between updates. This part works, in that I can display the response on the phone, and my server registers the user's action. Similarly, the trip is closed server-side upon the close trip request. However, when I tried starting a periodic tracking method from inside the StartTrack Activity, using requestLocationUpdates(String provider, long minTime, float minDistance, LocationListener listener) where minTime is the poll period from the server, it just did not work, and I'm not getting any errors. So it means I'm clueless at this point, never having used Android before. I have seen many posts here on using background services with handlers, pending intents, and other things to do similar stuff, but I really don't understand how to do it. I would like the user to do other stuff on the phone while the updates are going on, so if you guys could point me to a tutorial that shows how to actually write background services (maybe these run as separate classes?) or other ways of doing this, that would be great. Thanks!

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• C# wrapper for objects

  - by Haggai

  I'm looking for a way to create a generic wrapper for any object. The wrapper object will behave just like the class it wraps, but will be able to have more properties, variable, methods etc., for e.g. object counting, caching etc. Say the wrapper class be called Wrapper, and the class to be wrapped be called Square and has the constructor Square(double edge_len) and the properties/methods EdgeLength and Area, I would like to use it as follows: Wrapper<Square> mySquare = new Wrapper<Square>(2.5); /* or */ new Square(2.5); Console.Write("Edge {0} -> Area {1}", mySquare.EdgeLength, mySquare.Area); Obviously I can create such a wrapper class for each class I want to wrap, but I'm looking for a general solution, i.e. Wrapper<T> which can handle both primitive and compound types (although in my current situation I would be happy with just wrapping my own classes). Suggestions? Thanks.

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• what is the best practice approach for n-tier application development with entity framework?

  - by samsur

  I am building an application using entity framework. I am using the T4 template to generate self tracking entities. Currently, I am thinking of creating the entity framework code in a separate project. In this same project, I would have partial classes with additional methods for the entities. I am thinking of creating a separate project for a service layer (WCF) with methods for the upper/presentation tier. The WCF layer will reference the entity framework project. The methods in the WCF layer will return the entities or accept the entities as the parameters. I am thinkg of creating a third project for the presentation layer (ASP.net), this will make calls to the WCF service but will also need to reference the entities as the WCF methods take these types as the parameters/return types. In short, i want to use the STE entities generated by the T4 template as a DTO to be used in all layers. I was originally thinking of creating a business logic layer that maps to each entities. Example: If i have a customer class, the Business Layer would have a CustomerBLL class and then methods in the customerBLL will be used by the service layer. I was also trying to create a DTO in this business layer. I however found that this approach is very time consuming and i do not see a major benefit as it would create more maintenance work. What is the best practice for n-tier application development using entity framework 4?

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• Am I doing AS3 reference cleanup correctly?

  - by Ólafur Waage

  In one frame of my fla file (let's call it frame 2), I load a few xml files, then send that data into a class that is initialized in that frame, this class creates a few timers and listeners. Then when this class is done doing it's work. I call a dispatchEvent and move to frame 3. This frame does some things as well, it's initialized and creates a few event listeners and timers. When it's done, I move to frame 2 again. This is supposed to repeat as often as I need so I need to clean up the references correctly and I'm wondering if I'm doing it correctly. For sprites I do this. world.removeChild(Background); // world is the parent stage Background = null; For instances of other classes I do this. Players[i].cleanUp(world); // do any cleanup within the instanced class world.removeChild(PlayersSelect[i]); For event listeners I do this. if(Background != null) { Background.removeEventListener(MouseEvent.CLICK, deSelectPlayer); } For timers I do this. if(Timeout != null) { Timeout.stop(); Timeout.removeEventListener(TimerEvent.TIMER, queueHandler); Timeout.removeEventListener(TimerEvent.TIMER_COMPLETE, queueCompleted); Timeout = null; } And for library images I do this if(_libImage!= null) { s.removeChild(Images._libImage); // s is the stage _libImage= null; } And for the class itself in the main timeline, I do this Frame2.removeEventListener("Done", IAmDone); Frame2.cleanUp(); // the cleanup() does all the stuff above Frame2= null; Even if I do all this, when I get to frame 2 for the 2nd time, it runs for 1-2 seconds and then I get a lot of null reference errors because the cleanup function is called prematurely. Am I doing the cleanup correctly? What can cause events to fire prematurely?

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• Can I write a .NETCF Partial Class to extend System.Windows.Forms.UserControl?

  - by eidylon

  Okay... I'm writing a .NET CF (VBNET 2008 3.5 SP1) application, which has one master form, and it dynamically loads specific UserControls based on menu click, in a sort of framework idea. There are certain methods and properties these controls all need to work within the app. Right now I am doing this as an Interface, but this is aggravating as all get up, because some of the methods are optional, and yet I MUST implement them by the nature of interfaces. I would prefer to use inheritance, so that I can have certain code be inherited with overridability, but if I write a class which inherits System.Windows.Forms.UserControl and then inherit my control from that, it squiggles, and tells me that UserControls MUST inherit directly from System.Windows.Forms.UserControl. (Talk about a design flaw!) So next I thought, well, let me use a partial class to extend System.Windows.Forms.UserControl, but when I do that, even though it all seems to compile fine, none of my new properties/methods show up on my controls. Is there any way I can use partial classes to 'extend' System.Windows.Forms.UserControl? For example, can anyone give me a code sample of a partial class which simply adds a MyCount As Integer readonly property to the System.Windows.Forms.UserControl class? If I can just see how to get this going, I can take it from there and add the rest of my functionality. Thanks in advance! I've been searching google, but can't find anything that seems to work for UserControl extension on .NET CF. And the Interface method is driving me crazy as even a small change means updating ALL the controls whether they need to 'override' the method or not.

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• Starting a code library.

  - by Rob Stevenson-Leggett

  Hi, I've been meaning to start a library of reusable code snippets for a while and never seem to get round to it. I think my main problems are: Where to start. What structure should my library take? Should it be a compiled library (where appropriate or just classes I can drop into any project? Or a library project that can be included? In my experience, a built library will quickly become out of date and the source will get lost. So I'm leaning towards source libraries that I can export from SVN and include in any project. Intellectual property. I am employeed, so a lot of the code I write is not my IP. How can I ensure that I don't give my own IP away using it on projects in work and at home? I'm thinking the best way would be to licence my library with an open source licence and make sure I only add to it in my own time using my own equipment and therefore making sure that if I use it in a work project the same rules apply as if I was using a third party library. I write in many different languages and often would require two or more parts of this library. Should I look at implementing a few template projects and a core project for each of my chosen reusable components and languages? Has anyone else got this sort of library and how do you organise and update it?

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• How can I take advantage of IObservable/IObserver to get rid of my "god object"?

  - by Will

  In a system I'm currently working on, I have many components which are defined as interfaces and base classes. Each part of the system has some specific points where they interact with other parts of the system. For example, the data readying component readies some data which eventually needs to go to the data processing portion, the communications component needs to query different components for their status for relaying to the outside, etc. Currently, I glue these parts of the system together using a "god object", or an object with intimate knowledge of different parts of the system. It registers with events over here and shuttles the results to methods over there, creates a callback method here and returns the result of that method over there, and passes many requests through a multi-threaded queue for processing because it "knows" certain actions have to run on STA threads, etc. While its convenient, it concerns me that this one type knows so much about how everybody else in the system is designed. I'd much prefer a more generic hub that can be given instances which can expose events or methods or callbacks or that can consume these. I've been seeing more about the IObservable/IObserver features of the reactive framework and that are being rolled into .NET 4.0 (I believe). Can I leverage this pattern to help replace my "god object"? How should I go about doing this? Are there any resources for using this pattern for this specific purpose?

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• How did My Object Get into ASP.NET Page State?

  - by Paul Knopf

  I know what this error is, how to fix it, etc. My question is that I don't know why my current page I am developing is throwing this error when I am not using the foo class directly in any way, nor am I setting anything to the viewstate. I am using postbacks alot, but like I said, I am not storing anything in the viewstate etc one integer. I am using nhibernate if that is relevant. Any idea why I need to mark this classes as serializable that arent being used? Where should I start investigating? [SerializationException: Type 'FlexiCommerce.Persistence.NH.ContentPersister' in Assembly 'FlexiCommerce.Persistence.NH, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable.] System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType type) +9434541 System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type type, StreamingContext context) +247 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo() +160 System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder) +218 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo) +388 System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +444 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +133 System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph) +13 System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +2937 [ArgumentException: Error serializing value 'Music#2' of type 'FlexiCommerce.Components.Category.'] System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +3252 System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +2276 [ArgumentException: Error serializing value 'System.Object[]' of type 'System.Object[].'] System.Web.UI.ObjectStateFormatter.SerializeValue(SerializerBinaryWriter writer, Object value) +3252 System.Web.UI.ObjectStateFormatter.Serialize(Stream outputStream, Object stateGraph) +116 System.Web.UI.ObjectStateFormatter.Serialize(Object stateGraph) +57 System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Serialize(Object state) +4 System.Web.UI.Util.SerializeWithAssert(IStateFormatter formatter, Object stateGraph) +37 System.Web.UI.HiddenFieldPageStatePersister.Save() +79 System.Web.UI.Page.SavePageStateToPersistenceMedium(Object state) +108 System.Web.UI.Page.SaveAllState() +315 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2492

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• Maven + AspectJ - all steps to configure it

  - by Alice

  I have a problem with applying aspects to my maven project. Probably I am missing something, so I've made a list of steps. Could you please check if it is correct? Let say in projectA is an aspect class and in projectB classes, which should be changed by aspects. Create maven project ProjectA with AspectJ class add Aspectj plugin and dependency Add ProjectA as a dependency to projectB pom.xml Add to projectB pom.xml plugin " <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>aspectj-maven-plugin</artifactId> <version>1.4</version> <executions> <execution> <goals> <goal>compile</goal> <goal>test-compile</goal> </goals> </execution> </executions> <configuration> <source>${maven.compiler.source}</source> <target>${maven.compiler.target}</target> <aspectLibraries> <aspectLibrary> <groupId>ProjectA</groupId> <artifactId>ProjectA</artifactId> </aspectLibrary> </aspectLibraries> </configuration> </plugin> Add aspectj dependency After all these steps my problem is, that during compilation I get: [WARNING] advice defined in AspectE has not been applied [Xlint:adviceDidNotMatch] And then when I run my program: Exception in thread "FeatureExcutionThread" java.lang.NoClassDefFoundError: AspectE

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• Visual Studio: Collapse Methods, but not Comments (Summary etc.)

  - by Alex

  Hello, is there a way (settings? "macro"? extension?) that I can simply toggle outlining so that only the using section and my methods collapse to their signature line, but my comments (summary and double slash comments) and classes stay expanded? Examples: 1) Uncollapsed using System; using MachineGun; namespace Animals { /// <summary> /// Angry animal /// Pretty Fast, too /// </summary> public partial class Lion { // // Dead or Alive public Boolean Alive; /// <summary> /// Bad bite /// </summary> public PieceOfAnimal Bite(Animal animalToBite) { return animalToBite.Shoulder; } /// <summary> /// Fatal bite /// </summary> public PieceOfAnimal Kill(Animal animalToKill) { return animalToKill.Head; } } } 2) Collapsed (the following is my desired result): using[...] namespace Animals { /// <summary> /// Angry animal /// Pretty Fast, too /// </summary> public partial class Lion { // // Dead or Alive public Boolean Alive; /// <summary> /// Bad bite /// </summary> public PieceOfAnimal Bite(Animal animalToBite)[...] /// <summary> /// Fatal bite /// </summary> public PieceOfAnimal Kill(Animal animalToKill)[...] } } This is how I prefer seeing my class files (the collapsed form). I've been doing the collapsing by hand a million times by now and I think there should be a way to automate/customize/extend VS to do it the way I want? Every time I debug/hit a breakpoint, it uncollapses and messes up things. If I collapse via the context menu's collapse to outline etc. it also collapses my comments which isn't desired. Appreciate your help!

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• What's the correct way to pass parameters from VBScript to COM interface implemented in C#?

  - by nopopem

  I'm trying to expose a fairly simple C# class to COM which should be usable from VBScript (among others). Some objects need to be created via COM calls and will be used in furter calls later on. The definition of the exposed classes and interfaces looks like this: namespace Test { [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IComInterface { IFoo CreateFoo(); void UseFoo(int x, IFoo f); } [ClassInterface(ClassInterfaceType.None)] public sealed class CComInterface : IComInterface { public CComInterface() {} public IFoo CreateFoo() { return new Foo(); } public void UseFoo(int x, IFoo f) { f.Bar(); } } [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IFoo { void Bar(); } [ClassInterface(ClassInterfaceType.None)] public class Foo : IFoo { internal Foo() {} public void Bar() {} } } The simplest thinkable COM client in VBScript does this: Dim ci Set ci = WScript.CreateObject("Test.CComInterface") Dim foo Set foo = ci.CreateFoo foo.Bar ci.UseFoo 0, foo While the call to Bar succeeds, calling UseFoo fails with "Error 5: invalid procedure call or invalid argument" The generated IDL seems ok to me: dispinterface IComInterface { properties: methods: [id(0x60020003)] IFoo* CreateFoo(); [id(0x60020004)] void UseFoo( [in] long x, [in] IFoo* f); }; The vbs call succeeds when I wrap the second parameter in parentheses like this: ci.UseFoo 0, (foo) As far as I understand (I'm no VBScript expert however) this forces the reference to foo to be passed by value, i.e. a copy of the reference is being made. How can I change the interface so that it can be called with the foo reference directly? Since this will be a public interface used by customers I don't like the idea of having to explain why all the objects created need to be passed back in an extra pair of parentheses...

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• JPA returning null for deleted items from a set

  - by Jon

  This may be related to my question from a few days ago, but I'm not even sure how to explain this part. (It's an entirely different parent-child relationship.) In my interface, I have a set of attributes (Attribute) and valid values (ValidValue) for each one in a one-to-many relationship. In the Spring MVC frontend, I have a page for an administrator to edit these values. Once it's submitted, if any of these fields (as <input> tags) are blank, I remove the ValidValue object like so: Set<ValidValue> existingValues = new HashSet<ValidValue>(attribute.getValidValues()); Set<ValidValue> finalValues = new HashSet<ValidValue>(); for(ValidValue validValue : attribute.getValidValues()) { if(!validValue.getValue().isEmpty()) { finalValues.add(validValue); } } existingValues.removeAll(finalValues); for(ValidValue removedValue : existingValues) { getApplicationDataService().removeValidValue(removedValue); } attribute.setValidValues(finalValues); getApplicationDataService().modifyAttribute(attribute); The problem is that while the database is updated appropriately, the next time I query for the Attribute objects, they're returned with an extra entry in their ValidValue set -- a null, and thus, the next time I iterate through the values to display, it shows an extra blank value in the middle. I've confirmed that this happens at the point of a merge or find, at the point of "Execute query ReadObjectQuery(entity.Attribute). Here's the code I'm using to modify the database (in the ApplicationDataService): public void modifyAttribute(Attribute attribute) { getJpaTemplate().merge(attribute); } public void removeValidValue(ValidValue removedValue) { ValidValue merged = getJpaTemplate().merge(removedValue); getJpaTemplate().remove(merged); } Here are the relevant parts of the entity classes: Entity @Table(name = "attribute") public class Attribute { @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "attribute") private Set<ValidValue> validValues = new HashSet<ValidValue>(0); } @Entity @Table(name = "valid_value") public class ValidValue { @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "attr_id", nullable = false) private Attribute attribute; }

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• Facebook-ios-sdk with embedded UIWebView

  - by Benchtop Creative

  I'm working with the new facebook-ios-sdk and have successfully integrated the api into my native app. I am able to authenticate a user and properly setup permissions using a popup dialog with the ios-sdk classes. For a portion of my app I need to use the facebook connection within a UIWebView, using javascript and html to process data within the webview. Given that the user is already logged in and authenticated via the above routine, I would have assumed that the UIWebView would share those credentials, or that there would at least be some way to pass or assign the credentials to the webview. Unfortunately, I found this earlier post which seems to suggest that this scheme doesn't quite work (iOS - being logged-in in a webView after logging in with the SDK). Has anyone else encountered this and/or found a work around? This seems like it would be a fairly straightforward use case given that I'm not trying to launch mobile safari or something like that - it's all within the same native app. It just seems like there must be some sort of easy trick or setting that I'm missing. Maybe somehow setting cookies in the new UIWebView? or something like this?

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• Help C++ifying this C style code.

  - by Flamewires

  Hey I'm used to developing in C and I would like to use C++ in a project. Can anyone give me an example of how I would translate this C-style code into C++ code. I know it should compile in a c++ complier but I'm talking using c++ techniques(I.e. classes, RAII) typedef struct Solution Solution; struct Solution { double x[30]; int itt_found; double value; }; Solution *NewSolution() { Solution *S = (Solution *)malloc(sizeof(Solution)); for (int i=0;<=30;i++) { S-x[i] = 0; } S-itt_found = -1; return S; } void FreeSolution(Solution *S) { if (S != NULL) free(S); } int main() { Solution *S = NewSolution(); S-value = eval(S-x);// evals is another function that returns a double S-itt_found = 0; FreeSolution(S); return EXIT_SUCCESS; } Ideally I would like to be able to so something like this in main, but I'm not sure exactly how to create the class, i've read a lot of stuff but incorporating it all together correctly seems a little hard atm. Solution S(30);//constructor that takes as an argument the size of the double array S.eval();//a method that would run eval on S.x[] and store result in S.value cout << S.value << endl; Ask if you need more info, thanks.

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• C++: Construction and initialization order guarantees

  - by Helltone

  Hi, I have some doubts about construction and initialization order guarantees in C++. For instance, the following code has four classes X, Y, Z and W. The main function instantiates an object of class X. X contains an object of class Y, and derives from class Z, so both constructors will be called. Additionally, the const char* parameter passed to X's constructor will be implicitly converted to W, so W's constructor must also be called. What are the guarantees the C++ standard gives on the order of the calls to the copy constructors? Or, equivalently, this program is allowed to print? #include <iostream> class Z { public: Z() { std::cout << "Z" << std::endl; } }; class Y { public: Y() { std::cout << "Y" << std::endl; } }; class W { public: W(const char*) { std::cout << "W" << std::endl; } }; class X : public Z { public: X(const W&) { std::cout << "X" << std::endl; } private: Y y; }; int main(int, char*[]) { X x("x"); return 0; }

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• C++ iterator and const_iterator problem for own container class

  - by BaCh

  Hi there, I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem. It consists of a container class and two test classes: one test class using a std:vector which compiles nicely and the second test class which tries to use my own container class in exact the same way but fails miserably to compile. #include <vector> #include <algorithm> #include <iterator> using namespace std; template <typename T> class MyContainer { public: class iterator { public: typedef iterator self_type; inline iterator() { } }; class const_iterator { public: typedef const_iterator self_type; inline const_iterator() { } }; iterator begin() { return iterator(); } const_iterator begin() const { return const_iterator(); } }; // This one compiles ok, using std::vector class TestClassVector { public: void test() { vector<int>::const_iterator I=myc.begin(); } private: vector<int> myc; }; // this one fails to compile. Why? class TestClassMyContainer { public: void test(){ MyContainer<int>::const_iterator I=myc.begin(); } private: MyContainer<int> myc; }; int main(int argc, char ** argv) { return 0; } gcc tells me: test2.C: In member function ‘void TestClassMyContainer::test()’: test2.C:51: error: conversion from ‘MyContainer::iterator’ to non-scalar type ‘MyContainer::const_iterator’ requested I'm not sure where and why the compiler wants to convert an iterator to a const_iterator for my own class but not for the STL vector class. What am I doing wrong?

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• Entity Framework Validation & usage

  - by kmsellers

  I'm aware there is an AssociationChanged event, however, this event fires after the association is made. There is no AssociationChanging event. So, if I want to throw an exception for some validation reason, how do I do this and get back to my original value? Also, I would like to default values for my entity based on information from other entities but do this only when I know the entitiy is instanced for insertion into the database. How do I tell the difference between that and the object getting instanced because it is about to be populated based on existing data? Am I supposed to know? Is that considiered business logic that should be outside of my entity business logic? If that's the case, then should I be designing controller classes to wrap all these entities? My concern is that if I deliver back an entity, I want the client to get access to the properties, but I want to retain tight control over validations on how they are set, defaulted, etc. Every example I've seen references context, which is outside of my enity partial class validation, right? BTW, I looked at the EFPocoAdapter and for the life of me cannot determine how to populate lists of from within my POCO class... anyone know how I get to the context from a EFPoco Class?

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• Constructor and Destructors in C++ work?

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• Cocoa NSTextField Drag & Drop Requires Subclass... Really?

  - by ipmcc

  Until today, I've never had occasion to use anything other than an NSWindow itself as an NSDraggingDestination. When using a window as a one-size-fits-all drag destination, the NSWindow will pass those messages on to its delegate, allowing you to handle drops without subclassing NSWindow. The docs say: Although NSDraggingDestination is declared as an informal protocol, the NSWindow and NSView subclasses you create to adopt the protocol need only implement those methods that are pertinent. (The NSWindow and NSView classes provide private implementations for all of the methods.) Either a window object or its delegate may implement these methods; however, the delegate’s implementation takes precedence if there are implementations in both places. Today, I had a window with two NSTextFields on it, and I wanted them to have different drop behaviors, and I did not want to allow drops anywhere else in the window. The way I interpret the docs, it seems that I either have to subclass NSTextField, or make some giant spaghetti-conditional drop handlers on the window's delegate that hit-checks the draggingLocation against each view in order to select the different drop-area behaviors for each field. The centralized NSWindow-delegate-based drop handler approach seems like it would be onerous in any case where you had more than a small handful of drop destination views. Likewise, the subclassing approach seems onerous regardless of the case, because now the drop handling code lives in a view class, so once you accept the drop you've got to come up with some way to marshal the dropped data back to the model. The bindings docs warn you off of trying to drive bindings by setting the UI value programmatically. So now you're stuck working your way back around that too. So my question is: "Really!? Are those the only readily available options? Or am I missing something straightforward here?" Thanks.

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• Concurrency problem with arrays (Java)

  - by Johannes

  For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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