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• c++ "interface"-like classes similar to Java?

  - by William the Coderer

  In Java, you can define an interface as a class with no actual code implementation, but only to define the methods that a class must implement. Those types can be passed as parameters to methods and returned from methods. In C++, a pure virtual class can't be used as a parameter or return type, from what I can tell. Any way to mimic Java's interface classes? I have a string class in C++, and several subclasses for different encodings (like UTFxxx, ISOxxx, etc) that derive from the base string class. However, since there are so many different encodings, the base class has no meaningful implementation. But it would serve well as an interface if I could handle it as its own object and calls to that object would call on the correct subclass it was inherited to.

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• c struct map to ruby using SWIG

  - by pierr

  Hi, Is there any body can confirm the description here is true? My experience is that I can not use Example::Vector.new at all. C/C++ structs are wrapped as Ruby classes, with accessor methods (i.e. "getters" and "setters") for all of the struct members. For example, this struct declaration: struct Vector { double x, y; }; gets wrapped as a Vector class, with Ruby instance methods x, x=, y and y=. These methods can be used to access structure data from Ruby as follows: $ irb irb(main):001:0> require 'Example' true irb(main):002:0> f = Example::Vector.new #<Example::Vector:0x4020b268> irb(main):003:0> f.x = 10 nil irb(main):004:0> f.x 10.0

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• Interface name as a Type

  - by user1889148

  I am trying to understand interfaces in Java and have this task to do which I am a stack with. It must be something easy, but I don't seem to see the solution. Interface contains a few methods, one of them should return true if all elements of this set are also in the set. I.e. public interface ISet{ //some methods boolean isSubsetOf(ISet x); } Then the class: public class myClass implements ISet{ ArrayList<Integer> mySet; public myClass{ mySet = new ArrayList<Integer>(); } //some methods public boolean isSubsetOf(ISet x){ //method body } } What do I need to write in method body? How do I check that the instance of myClass is a subset of ISet collection? I was trying to cast, but it gives an error: ArrayList<Integer> param = (ArrayList<Integer>)x; return param.containsAll(mySet);

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• Should I separate RESTful API controllers from "regular" controllers?

  - by keithjgrant

  This seems like an elementary question, but after a lot of searching around I can't seem to find a straightforward explanation: If I'm building a web application that is going to be accessed largely through a web browser, but that will also support some API requests in a RESTful way, should there be a large degree of separation between the two? On one hand, it seems a large amount of the functionality is the same, with identical data presented in different views (HTML vs. XML/JSON). But on the other hand, there are certain things I need to present to the browser that doesn't quite fit a RESTful approach: how to get an empty form to create a new instance of a resource and how to get a pre-populated form to edit an existing resource. Should these two different methods of accessing the system by funneled through different controllers? Different methods in the same controller? The exact same methods with a switch for view type?

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• Automatically decorating every instance method in a class

  - by max

  I want to apply the same decorator to every method in a given class, other than those that start and end with __. It seems to me it should be doable using a class decorator. Are there any pitfalls to be aware of? Ideally, I'd also like to be able to: disable this mechanism for some methods by marking them with a special decorator enable this mechanism for subclasses as well enable this mechanism even for methods that are added to this class in runtime [Note: I'm using Python 3.2, so I'm fine if this relies on features added recently.] Here's my attempt: _methods_to_skip = {} def apply(decorator): def apply_decorator(cls): for method_name, method in get_all_instance_methods(cls): if (cls, method) in _methods_to_skip: continue if method_name[:2] == `__` and method_name[-2:] == `__`: continue cls.method_name = decorator(method) return apply_decorator def dont_decorate(method): _methods_to_skip.add((get_class_from_method(method), method)) return method Here are things I have problems with: how to implement get_all_instance_methods function not sure if my cls.method_name = decorator(method) line is correct how to do the same to any methods added to a class in runtime how to apply this to subclasses how to implement get_class_from_method

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• Active Record's SessionScope in BL or DL ?

  - by StupidDeveloper

  Imagine that I have 3 projects: DL, BL and WS. DL contains Active Record implementation with all the mappings, BL has some logic (calling various DL methods) and finally WebService project exposes some BL methods (using some DTO mappings). The questions are: Should I put all data related methods in DL or is it allowed to use SessionScope in BL ? There are some complicated stuff that is right now done on BL. Should/can BL operate on classes-mappings of the Active record? The question is where should be the translation to DTO be made (at the BL level? ) ?

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• Java Interface Reflection Alternatives

  - by Phaedrus

  I am developing an application that makes use of the Java Interface as more than a Java interface, i.e., During runtime, the user should be able to list the available methods within the interface class, which may be anything: private Class<? extends BaseInterface> interfaceClass. At runtime, I would like to enum the available methods, and then based on what the user chooses, invoke some method. My question is: Does the Java "Interface" architecture provide any method for me to peek and invoke methods without using the Reflection API? I wish there were something like this (Maybe there is): private Interface<? extends BaseInterface> interfaceAPI; public void someMethod(){ interfaceAPI.listMethods(); interfaceAPI.getAnnotations(); } Maybe there is some way to use Type Generics to accomplish what I want? Thanks, Phaedrus

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• Optional parens in Ruby for method with uppercase start letter?

  - by RasmusKL

  I just started out using IronRuby (but the behaviour seems consistent when I tested it in plain Ruby) for a DSL in my .NET application - and as part of this I'm defining methods to be called from the DSL via define_method. However, I've run into an issue regarding optional parens when calling methods starting with an uppercase letter. Given the following program: class DemoClass define_method :test do puts "output from test" end define_method :Test do puts "output from Test" end def run puts "Calling 'test'" test() puts "Calling 'test'" test puts "Calling 'Test()'" Test() puts "Calling 'Test'" Test end end demo = DemoClass.new demo.run Running this code in a console (using plain ruby) yields the following output: ruby .\test.rb Calling 'test' output from test Calling 'test' output from test Calling 'Test()' output from Test Calling 'Test' ./test.rb:13:in `run': uninitialized constant DemoClass::Test (NameError) from ./test.rb:19:in `<main>' I realize that the Ruby convention is that constants start with an uppercase letter and that the general naming convention for methods in Ruby is lowercase. But the parens are really killing my DSL syntax at the moment. Is there any way around this issue?

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• Refactoring method that was previously injected with implement

  - by ryber

  Greetings, I'm trying to override or extend the Element.show() and .hide() methods in mootools in order to add some WAI-Aria toggling. I was trying to use the Class.Refactor() method like this: Element = Class.refactor(Element, { show: function(displayString) { result = this.previous(displayString); // Do my thing return result; }, hide: function() { result = this.previous(); // Do my thing return result; } }); however, this is not working, previous is null and I think the reason is that Mootools injects those methods through Element.implement. So the methods are not native? I have figured out how to completely replace .show and .hide but I would like to retain all of their existing functionality and just add to it. Any ideas?

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• Can I use the decorator pattern to wrap a method body?

  - by mgroves

  I have a bunch of methods with varying signatures. These methods interact with a fragile data connection, so we often use a helper class to perform retries/reconnects, etc. Like so: MyHelper.PerformCall( () => { doStuffWithData(parameters...) }); And this works fine, but it can make the code a little cluttery. What I would prefer to do is decorate the methods that interact with the data connection like so: [InteractsWithData] protected string doStuffWithData(parameters...) { // do stuff... } And then essentially, whenever doStuffWithData is called, the body of that method would be passed in as an Action to MyHelper.PerformCall(). How do I do this?

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• In Java how instance of and type cast(i.e (ClassName)) works on proxy object ?

  - by learner

  Java generates a proxy class for a given interface and provides the instance of the proxy class. But when we type cast the proxy object to our specific Object, how java handles this internally? Is this treated as special scenario? For example I have class 'OriginalClass' and it implements 'OriginalInterface', when I create proxy object by passing 'OriginalInterface' interface java created proxy class 'ProxyClass' using methods in the provided interface and provides object of this class(i.e ProxyClass). If my understanding is correct then can you please answer following queries 1) When I type cast object of ProxyClass to my class OriginalClass this works, but how java is allowing this? Same in case of instace of? 2) As my knowledge java creates a proxy class only with the methods, but what happen when I try to access attributes on this object? 3) Only interface methods are getting implemented in Proxy, but what happens when I try to access a method which not in interface and only mentioned in the class? Thanks, Student

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• Examples of both beautiful and ugly java code?

  - by tputkonen

  I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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• Using a part of a class in multiple projects

  - by Axarydax

  I have a set of methods that do some utility work over SQL connection, and until now these have been copied over from project to project. But as time goes on, project numbers have grown and I need to keep these methods in sync in case I find a bug or need to update it. I have managed to get it to the state that SQL access class is a partial class, one part is specific for project and contains wrappers for a specific database. The second part is the common one and contains methods that are used in all project-specific databases. The problem is that now I would have the "utility" class copied over 8 projects, with the same content, but in different namespaces. In C/C++ it would have been simple, because I would just have #included the contents of the file wherever needed. What should I do in C#?

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• Does C++ require a destructor call for each placement new?

  - by Josh Haberman

  I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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• Is there a design pattern for this ?

  - by ytrewq

  I have a component that needs to call a specific service depending on the input it receives. So my component has to look at the input and based on a configuration that says "for this input call this service with this data" needs to call the proper service. The services have a common signature method and a specific one (each). I thought about an abstract class that includes the signatures for all three methods. The implementation for the two services will override all three methods (throwing NotImplementedException for the methods that are not supported by current service). A component that could be initialized with a map (that for each input type will have the type of the service to be called) will also be defined. Do you have a better approach to cope this scenario ?

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• Why isn't the eigenclass equivalent to self.class, when it looks so similar?

  - by The Wicked Flea

  I've missed the memo somewhere, and I hope you'll explain this to me. Why is the eigenclass of an object different from self.class? class Foo def initialize(symbol) eigenclass = class << self self end eigenclass.class_eval do attr_accessor symbol end end end My train of logic that equates the eigenclass with class.self is rather simple: class << self is a way of declaring class methods, rather than instance methods. It's a shortcut to def Foo.bar. So within the reference to the class object, returning self should be identical to self.class. This is because class << self would set self to Foo.class for definition of class methods/attributes. Am I just confused? Or, is this a sneaky trick of Ruby meta-programming?

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• Error handling in controllers with MVC

  - by twrn

  Does it make sense to do error handling and logging inside actions methods or handle the OnException method inside the controllers. One way means writing try/catches in all the action methods even when there is nothing to be done to recover from the error. Handling this at the controller level would allow logging and redirection to an error handler page without writing try/catches inside all the action methods. Which method makes the most sense? Here is example code of try/catches in an action method. [HttpPost] public ActionResult Delete(int id) { using (new Tracer("Project Controller")) { try { Logger.Write("Deleting project"); projService.DeleteProject(id); TempData["message"] = "Project Deleted successfully"; } catch (System.Exception ex) { HandleException(ex, "Project could not be deleted."); } return RedirectToAction("List"); } }

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• Merging and splitting overlapping rectangles to produce non-overlapping ones

  - by uj

  I am looking for an algorithm as follows: Given a set of possibly overlapping rectangles (All of which are "not rotated", can be uniformly represented as (left,top,right,bottom) tuplets, etc...), it returns a minimal set of (non-rotated) non-overlapping rectangles, that occupy the same area. It seems simple enough at first glance, but prooves to be tricky (at least to be done efficiently). Are there some known methods for this/ideas/pointers? Methods for not necessarily minimal, but heuristicly small, sets, are interesting as well, so are methods that produce any valid output set at all.

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• Class.Class vs Namespace.Class for top level general use class libraries?

  - by Joan Venge

  Which one is more acceptable (best-practice)?: namespace NP public static class IO public static class Xml ... // extension methods using NP; IO.GetAvailableResources (); vs public static class NP public static class IO public static class Xml ... // extension methods NP.IO.GetAvailableResources (); Also for #2, the code size is managed by having partial classes so each nested class can be in a separate file, same for extension methods (except that there is no nested class for them) I prefer #2, for a couple of reasons like being able to use type names that are already commonly used, like IO, that I don't want to replace or collide. Which one do you prefer? Any pros and cons for each? What's the best practice for this case? EDIT: Also would there be a performance difference between the two?

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• [C++] Simple inheritance question

  - by xbonez

  I was going over some sample questions for an upcoming test, and this question is totally confusing me. Any help would be appreciated. Consider the following code: class GraduateStudent : public Student { ... }; If the word "public" is omitted, GraduateStudent uses private inheritance, which means which of the following? GraduateStudent objects may not use methods of Student. GraduateStudent does not have access to private objects of Student. No method of GraduateStudent may call a method of Student. Only const methods of GraduateStudent can call methods of Student.

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• Rotating Viewbox contents smoothly

  - by user204562

  I'm looking to teach myself better methods of doing things in WPF that I would normally do manually. In this case, I have a ViewBox with an image in it. I also have a button that uses a DoubleAnimation to rotate the image 90 to the right. This animation works fine, but obviously because it's square as it turns, the image does a "best fit" to the ViewBox which makes the rotation look quite bad, as it gets larger and smaller as its longest edge shrinks or grows to fit to that particular rotation angle. I am looking for any advice on the best way to handle this using appropriate WPF methods. Obviously I could do all the calculations manually, but I would be more interested in finding a way to use the controls and methods built into the .NET architecture. Thanks for your help.

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• How to access the service instance from host object in WCF?

  - by user1048677

  I am trying to incarnate some sort of ad hoc WCF service. I already managed to launch it and make it call its own web methods as some other guy's methods. The issue that I am facing is instance management. I have set [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)] so it now has a global instance with the same properties for all clients. But besides that I need it to call other services of its kind while listening to incoming requests from clients (similar crazy services). While debugging I noticed that the ServiceHost's constructor calls the constructor of the service class. So, I assumed it has access to the global instance of this class and I need to find a way to call methods of this instance. Please don't ask what I have been smoking, I just have to make it ad hoc.

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• F# in ASP.NET, mathematics and testing

  - by DigiMortal

  Starting from Visual Studio 2010 F# is full member of .NET Framework languages family. It is functional language with syntax specific to functional languages but I think it is time for us also notice and study functional languages. In this posting I will show you some examples about cool things other people have done using F#. F# and ASP.NET As I am ASP/ASP.NET MVP I am – of course – interested in how people use different languages and technologies with ASP.NET. C# MVP Tomáš Petrícek writes about developing ASP.NET MVC applications using F#. He also shows how to use LINQ To SQL in F# (using F# PowerPack) and provides sample solution and Visual Studio 2010 template for F# MVC web applications. You may also find interesting how you can create controllers in F#. Excellent work, Tomáš! Vladimir Matveev has interesting example about how to use F# and ApplicationHost class to process ASP.NET requests ouside of IIS. This is simple and very straight-forward example and I strongly suggest you to take a look at it. Very cool example is project Strom in Codeplex. Storm is web services testing tool that is fully written on F#. Take a look at this site because Codeplex offers also source code besides binaries. Math Functional languages are strong in fields like mathematics and physics. When I wrote my C# example about BigInteger class I found out that recursive version of Fibonacci algorithm in C# is not performing well. In same time I made same experiment on F# and in F# there were no performance problems with recursive version. You can find F# version of Fibonacci algorithm from Bob Palmer’s blog posting Fibonacci numbers in F#. Although golden spiral is useful for solving many problems I looked for some practical code example and found one. Kean Walmsley published in his Through the Interface blog very interesting posting Creating Fibonacci spirals in AutoCAD using F#. There are also other cool examples you may be interested in. Using numerical components by Extreme Optimization  it is possible to make some numerical integration (quadrature method) using F# (also C# example is available). fsharp.it introduces factorials calculation on F#. Robert Pickering has made very good work on programming The Game of Life in Silverlight and F# – I definitely suggest you to try out this example as it is very illustrative too. Who wants something more complex may take a look at Newton basin fractal example in F# by Jonathan Birge. Testing After some searching and surfing I found out that there is almost everything available for F# to write tests and test your F# code. FsCheck - FsCheck is a port of Haskell's QuickCheck. Important parts of the manual for using FsCheck is almost literally "adapted" from the QuickCheck manual and paper. Any errors and omissions are entirely my responsibility. FsTest - This project is designed to Language Oriented Programming constructs around unit testing and behavior testing in F#. The goal of this project is to create a Domain Specific Language for testing F# code in a way that makes sense for functional programming. FsUnit - FsUnit makes unit-testing with F# more enjoyable. It adds a special syntax to your favorite .NET testing framework. xUnit.NET - xUnit.net is a developer testing framework, built to support Test Driven Development, with a design goal of extreme simplicity and alignment with framework features. It is compatible with .NET Framework 2.0 and later, and offers several runners: console, GUI, MSBuild, and Visual Studio integration via TestDriven.net, CodeRush Test Runner and Resharper. It also offers test project integration for ASP.NET MVC. Getting started Well, as a first thing you need Visual Studio 2010. Then take a look at these resources: F# samples @ MSDN Microsoft F# Developer Center @ MSDN F# Language Reference @ MSDN F# blog F# forums Real World Functional Programming: With Examples in F# and C# (Amazon) Happy F#-ing! :)

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• Guessing Excel Data Types

  - by AjarnMark

  Note to Self HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\4.0\Engines\Excel: TypeGuessRows = 0 means scan everything. Note to Others About 10 years ago I stumbled across this bit of information just when I needed it and it saved my project.  Then for some reason, a few years later when it would have been nice, but not critical, for some reason I could not find it again anywhere.  Well, now I have stumbled across it again, and to preserve my future self from nightmares and sudden baldness due to pulling my hair out, I have decided to blog it in the hopes that I can find it again this way. Here’s the story…  When you query data from an Excel spreadsheet, such as with old-fashioned DTS packages in SQL 2000 (my first reference) or simply with an OLEDB Data Adapter from ASP.NET (recent task) and if you are using the Microsoft Jet 4.0 driver (newer ones may deal with this differently) then you can get funny results where the query reports back that a cell value is null even when you know it contains data. What happens is that Excel doesn’t really have data types.  While you can format information in cells to appear like certain data types (e.g. Date, Time, Decimal, Text, etc.) that is not really defining the cell as being of a certain type like we think of when working with databases.  But, presumably, to make things more convenient for the user (programmer) when you issue a query against Excel, the query processor tries to guess what type of data is contained in each column and returns it in an appropriate manner.  This is all well and good IF your data is consistent in every row and matches what the processor guessed.  And, for efficiency’s sake, when the query processor is trying to figure out each column’s data type, it does so by analyzing only the first 8 rows of data (default setting). Now here’s the problem, suppose that your spreadsheet contains information about clothing, and one of the columns is Size.  Now suppose that in the first 8 rows, all of your sizes look like 32, 34, 18, 10, and so on, using numbers, but then, somewhere after the 8th row, you have some rows with sizes like S, M, L, XL.  What happens is that by examining only the first 8 rows, the query processor inferred that the column contained numerical data, and then when it hits the non-numerical data in later rows, it comes back blank.  Major bummer, and a real pain to track down if you don’t know that Excel is doing this, because you study the spreadsheet and say, “the data is RIGHT THERE!  WHY doesn’t the query see it?!?!”  And the hair-pulling begins. So, what’s a developer to do?  One option is to go to the registry setting noted above and change the DWORD value of TypeGuessRows from the default of 8 to 0 (zero).  Setting this value to zero will force Jet to scan every row in the spreadsheet before making its determination as to what type of data the column contains.  And that means that in the example above, it would have treated the column as a string rather than as numeric, and presto! your query now returns all of the values that you know are in there. Of course, there is a caveat… if you are querying large spreadsheets, making Jet scan every row can be quite a performance hit.  You could enter a different number (more than 8) that you believe is a better sampling of rows to make the guess, but you still have the possibility that every row scanned looks alike, but that later rows are different, and that you might get blanks when there really is data there.  That’s the type of gamble, I really don’t like to take with my data. Anyone with a better approach, or with experience with more recent drivers that have a better way of handling data types, please chime in!

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• Bitmask data insertions in SSDT Post-Deployment scripts

  - by jamiet

  On my current project we are using SQL Server Data Tools (SSDT) to manage our database schema and one of the tasks we need to do often is insert data into that schema once deployed; the typical method employed to do this is to leverage Post-Deployment scripts and that is exactly what we are doing. Our requirement is a little different though, our data is split up into various buckets that we need to selectively deploy on a case-by-case basis. I was going to use a SQLCMD variable for each bucket (defaulted to some value other than “Yes”) to define whether it should be deployed or not so we could use something like this in our Post-Deployment script: IF ($(DeployBucket1Flag) = 'Yes')BEGIN   :r .\Bucket1.data.sqlENDIF ($(DeployBucket2Flag) = 'Yes')BEGIN   :r .\Bucket2.data.sqlENDIF ($(DeployBucket3Flag) = 'Yes')BEGIN   :r .\Bucket3.data.sqlEND That works fine and is, I’m sure, a very common technique for doing this. It is however slightly ugly because we have to litter our deployment with various SQLCMD variables. My colleague James Rowland-Jones (whom I’m sure many of you know) suggested another technique – bitmasks. I won’t go into detail about how this works (James has already done that at Using a Bitmask - a practical example) but I’ll summarise by saying that you can deploy different combinations of the buckets simply by supplying a different numerical value for a single SQLCMD variable. Each bit of that value’s binary representation signifies whether a particular bucket should be deployed or not. This is better demonstrated using the following simple script (which can be easily leveraged inside your Post-Deployment scripts): /* $(DeployData) is a SQLCMD variable that would, if you were using this in SSDT, be declared in the SQLCMD variables section of your project file. It should contain a numerical value, defaulted to 0. In this example I have declared it using a :setvar statement. Test the affect of different values by changing the :setvar statement accordingly. Examples: :setvar DeployData 1 will deploy bucket 1 :setvar DeployData 2 will deploy bucket 2 :setvar DeployData 3   will deploy buckets 1 & 2 :setvar DeployData 6   will deploy buckets 2 & 3 :setvar DeployData 31  will deploy buckets 1, 2, 3, 4 & 5 */ :setvar DeployData 0 DECLARE  @bitmask VARBINARY(MAX) = CONVERT(VARBINARY,$(DeployData)); IF (@bitmask & 1 = 1) BEGIN     PRINT 'Bucket 1 insertions'; END IF (@bitmask & 2 = 2) BEGIN     PRINT 'Bucket 2 insertions'; END IF (@bitmask & 4 = 4) BEGIN     PRINT 'Bucket 3 insertions'; END IF (@bitmask & 8 = 8) BEGIN     PRINT 'Bucket 4 insertions'; END IF (@bitmask & 16 = 16) BEGIN     PRINT 'Bucket 5 insertions'; END An example of running this using DeployData=6 The binary representation of 6 is 110. The second and third significant bits of that binary number are set to 1 and hence buckets 2 and 3 are “activated”. Hope that makes sense and is useful to some of you! @Jamiet P.S. I used the awesome HTML Copy feature of Visual Studio’s Productivity Power Tools in order to format the T-SQL code above for this blog post.

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