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  • Dynamic Dispatch without Virtual Functions

    - by Kristopher Johnson
    I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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  • What are your references/recommendation on .NET DVDs, books and online training?

    - by egyamado
    There are lots of training methods from different vendors to learn .NET technologies (i.e. books, DVDs, online training, etc.). All of them claim the same thing: that they are the best, their content is 100% guaranteed, makes their customers professional in no time, etc. It’s confusing and sometimes frustrating as well. I especially want a training resource (i.e. a course) to provide valuable content in short time. More importantly I feel they should do their job properly so as to avoid the customer feeling they've wasted time or money. What I should do when I evaluating training methods and resources to help further software development skills? What are your training sources? Do you have any recommendations?

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  • Benefits of arrays

    - by Vitalii Fedorenko
    As I see it, the advantages of List over array are pretty obvious: Generics provide more precise typing: List<Integer>, List<? extends Number>, List<? super Integer>. List interface has a bunch useful methods: addAll, remove etc. While for arrays all standard operations except get/set must be performed in a procedure manner by passing it to a static method. Collections offer different implementations like ArrayList, LinkedList, unmodifieable and synchronized lists, which can be hidden under common List interface. OOB length control. As disadvantages I can only mention absence of syntactic sugar and runtime type check. At the same time supporting of both structures requires frequent using of asList and toArray methods, which makes code less readable. So I am curious if there are any important benefits of using arrays that I miss.

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  • Quartz 2D animating text?

    - by coure06
    i have to animate text around a circle. The text will also scale up/down. Whats the best approach to accomplish this? (i am using Quartz 2D) My approach is: -- Calculate point using sin and cos methods. -- Move Pen there and draw text with alpha and size. -- Clear the screen -- Calculate next point using sin and cos methods. -- Move pen there and draw text with alpha and size. -- clear the screen so on... any better way?

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  • Using the JNotify library, how can you tell if a deleted file was a file or a directory?

    - by Moeri
    For those unfamiliar with JNotify, this is a library which provides an easy way to monitor events in a directory. For instance, when a file gets deleted in the selected folder, the method "fileDeleted" gets called, along with a few parameters. Here's an example of the fileDeleted method: public void fileDeleted(int wd, String rootPath, String name) { print("deleted " + rootPath + " : " + name); } Now, I would like to know if the deleted file was a file or directory. My usual approach is to create a new File object with the given path, and use the methods isFile() and isDirectory() However, since this file is already deleted, these methods always return false. So here's my concrete question: I have the path to a deleted file or directory, how can I tell wether it was a file or a directory? Is there a workaround to this? What's the best practice to do here? Thank you in advance.

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  • Conceptual inheritance implementation

    - by TheSENDER
    Hi there, I'm writing a spatial data structure and I have a doubt about what's the best NODE implementation. According to my design I have an abstract node entity and three classes which inherit from it: EMPTYNODE, FULLNODE, INTERNALNODE. The first one has no particular data. The second one has 1 reference to a generic element. The third one has 2 references to other nodes. I have found several ways to implement this situation (that I have already coded) but I can't decide what's the best. The first solution that I have found is to use a single class Node that potentially performs all the operation in this way: private static class Node { private Elem elem = null; private Node left = null, right = null; public Elem getElem() { assert isFull(); return elem; } public boolean isEmpty() { return elem == null && left == null; } public boolean isFull() { return elem != null; } public boolean isInternal() { return elem == null && left != null; } } The second solution is to write an explicit division by classes where every class offers only its methods. Obviously in this way we are obliged to perform several casts to the node objects. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); } private static class FullNode extends Node{ private ITriangle elem; @Override public boolean isEmpty() { return false; } @Override public final boolean isFull() { return true; } @Override public final boolean isInternal() { return false; } public Elem getElem() { return elem; } } The third one solution is to use the inheritance allowing every classes to offer all the methods, but the object type should by check by "isEmpty()" and similar methods. In case of wrong call we'll throw an exception. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); public abstract Elem getElem(); } private static class Empty extends Node{ @Override public boolean isEmpty() { return true; } @Override public final boolean isFull() { return false; } @Override public final boolean isInternal() { return false; } @Override public Elem getElem() { throw new AssertionError(); } } What do you think about these three solutions? Which one would you use? Any other ideas? Thanks for your help. Every idea will be appreciated.

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  • How to set up dynamically Part in MultipartRequestEntity

    - by ee_vin
    Hello, I'm using commons-httpclient-3.1 inside my android application. And I would like to know if it possible to manipulate Part (org.apache.commons.httpclient.methods.multipart.Part) dynamically? Essentially adding new FilePart and new StringPart at runtime before sending the request. Every example I've found until now suppose that you know how many fields you are dealing with. Ex: File f = new File("/path/fileToUpload.txt"); PostMethod filePost = new PostMethod("http://host/some_path"); Part[] parts = { new StringPart("param_name", "value"), new FilePart(f.getName(), f) }; filePost.setRequestEntity( new MultipartRequestEntity(parts, filePost.getParams()) ); HttpClient client = new HttpClient(); int status = client.executeMethod(filePost); code from http://hc.apache.org/httpclient-3.x/apidocs/org/apache/commons/httpclient/methods/multipart/MultipartRequestEntity.html Android specific thread: http://groups.google.com/group/android-developers/browse_thread/thread/0f9e17bbaf50c5fc Thank you

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  • Looping differences in Ruby using Range vs. Times

    - by jbjuly
    I'm trying to solve a Project Euler problem using Ruby, I used 4 different looping methods, the for-loop, times, range and upto method, however the for-loop and times method only produces the expected answer, while the range and upto method does not. I'm assuming that they are somewhat the same, but I found out it's not. Can someone please explain the differences between these methods? Here's the looping structure I used # for-loop method for n in 0..1 puts n end 0 1 => 0..1 # times method 2.times do |n| puts n end 0 1 => 2 # range method (0..1).each do |n| puts n end 0 1 => 0..1 # upto method 0.upto(1) do |n| puts n end 0 1 => 0

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  • Model's method not being recognized when called

    - by Brian Roisentul
    I'm using ruby on rails 2.3.2 and also using the acts_as_taggable_on puglin. That generated me two db tables: tags and taggings. As I didn't need anything more from those, I didn't create a Tag model, for example. Now the project is more mature, I need to create some methods for tags, so I created a Tag model with some methods in it. The model looks something like this: class Tag < ActiveRecord::Base def self.get_parent parent = Tag.find(self.parent_id) return parent end end When I call it from a controller, it won't find the method. This is the code: tag = Tag.find(tag_id) the_parent = tag.get_parent This will throw an error saying: undefined method `get_parent' for #<Tag id: 13, name: "Historia", parent_id: 12> I don't know what's wrong. Any help will be appreciated.

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  • Beginner Design pattern question (Web Services involved)

    - by zombie
    Hi all ! I am a noob to web services world. I need to develop a login validator module and expose it as a service. I want it to be service independent, i.e I should have the option of exposing it as a SOAP service or REST service in the future. What pattern should I follow ? Sorry if I am unclear in my requirements, I can clarify as per need. Thanks !! Edit : I am using Eclipse as an IDE and Jersey libraries. I am not into any framework, simply using the MVC pattern. I find a lot of difference between SOAP ann REST methods, so I want my methods to be implementation independent - i.e I should be easily able to use my method through a SOAP or REST service call as per need. What should I do for maximum flexibility ?

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  • How to Map a table with another lookup table using JPA?

    - by Sameer Malhotra
    Hi, I have two tables: 1) Application(int appid, int statusid, String appname, String appcity with getter and Setter methods) 2) App_Status(int statusid,String statusDescription with setter and getter methods) I want to map Application table with App_Status so that I don't have to query separately App_Status table in order to get the statusDescription. One thing I have to careful is that no matter what (Insert,update or delete) to the Application table the App_Status table should be unaffected means its a read only table which is maintained by the DBA internally and used only for lookup table. I am using JPA annotations so please suggest how to handle this.

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  • Why does Cache.Add return an object that represents the cached item?

    - by Pure.Krome
    From MSDN about the differences between Adding or Inserting an item the ASP.NET Cache: Note: The Add and Insert methods have the same signature, but there are subtle differences between them. First, calling the Add method returns an object that represents the cached item, while calling Insert does not. Second, their behavior is different if you call these methods and add an item to the Cache that is already stored there. The Insert method replaces the item, while the Add method fails. [emphasis mine] The second part is easy. No question about that. But with the first part, why would it want to return an object that represents the cached item? If I'm trying to Add an item to the cache, I already have/know what that item is? I don't get it. What is the reasoning behind this?

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  • Is there a Java unit-test framework that auto-tests getters and setters?

    - by Michael Easter
    There is a well-known debate in Java (and other communities, I'm sure) whether or not trivial getter/setter methods should be tested. Usually, this is with respect to code coverage. Let's agree that this is an open debate, and not try to answer it here. There have been several blog posts on using Java reflection to auto-test such methods. Does any framework (e.g. jUnit) provide such a feature? e.g. An annotation that says "this test T should auto-test all the getters/setters on class C, because I assert that they are standard". It seems to me that it would add value, and if it were configurable, the 'debate' would be left as an option to the user.

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  • An exception to the "only one implementation" rule ?

    - by ereOn
    While I was reading the accepted answer of this question, I had the following question: Typically, methods are defined in header files (.hpp or whatever), and implementation in source files (.cpp or whatever). One of the main reasons it is bad practice to ever include a "source file" (#include <source_file.cpp>) is that its methods implementation would then be duplicated, resulting in linking errors. When one writes: #ifndef BRITNEYSPEARS_HPP #define BRITNEYSPEARS_HPP class BritneySpears { public: BritneySpears() {}; // Here the constructor has implementation. }; #endif /* BRITNEYSPEARS_HPP */ He is giving the implementation of the constructor (here an "empty" implementation, but still). But why then including this header file multiple times (aka. on different source files) will not generate a "duplicate definition" error at link time ?

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  • PHP5: restrict access to function to certain classes

    - by Tim
    Is there a way in PHP5 to only allow a certain class or set of classes to call a particular function? For example, let's say I have three classes ("Foo", "Bar", and "Baz"), all with similarly-named methods, and I want Bar to be able to call Foo::foo() but deny Baz the ability to make that call: class Foo { static function foo() { print "foo"; } } class Bar { static function bar() { Foo::foo(); print "bar"; } // Should work } class Baz { static function baz() { Foo::foo; print "baz"; } // Should fail } Foo::foo(); // Should also fail There's not necessarily inheritance between Foo, Bar, and Baz, so the use of protected or similar modifiers won't help; however, the methods aren't necessarily static (I made them so here for the simplicity of the example).

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  • Where's the definitive resource online about how to carry out Agile development?

    - by jdk
    I want to start Agile practices in a team. I'm assuming the information is available for free online about how to specifically carry it out. Online I can locate the manifesto, the alliances and corporations involved but where is the actual central guide or root instruction set about how to do it? (Maybe the practices themselves are more ethereal or subjective than I expect and it's found in multiple places?) Edit to summarize solutions: Agile is a concept so that's what's to be found online about it. However specific processes or methods of Agile development have been created like Scrum and Extreme programming to provide concrete solutions to teams who want to adopt Agile and reap its proposed benefits. Find the shoe (or method) that fits best. Maybe create it. If looking for solutions online to implement Agile development in your organization or for your project, seek out the specific methods too and decide among them.

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  • Connecting data to a GUI - OOP

    - by tau
    I have an application with several graphs and tables on it. I worked fast and just made classes like Graph and Table that each contained a request object (pseudo-code): class Graph { private request; public function setDateRange(dateRange) { request.setDateRange(dateRange); } public function refresh() { request.getData(function() { //refresh the display }); } } Upon a GUI event (say, someone changes the date range dropdown), I'd just call the setters on the Graph instance and then refresh it. Well, when I added other GUI elements like tables and whatnot, they all basically had similar methods (setDateRange and other things common to the request). What are some more elegant OOP ways of doing this? The application is very simple and I don't want to over-architect it, but I also don't want to have a bunch of classes with basically the same methods that are just routing to a request object. I also don't want to set up each GUI class as inheriting from the request class, but I'm open to any ideas really.

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  • How to call/use a value converter inverted

    - by Soko
    Is it possible to use a converter the "wrong" way around? In other words: can I swap source and target? Here's an example: I created a simple IValueConverter called NullableDecimalToStringConverter which converts an input if "" into null and a number into decimal. I use it to bind a TextBox in my WPF view to a decimal? property in my ViewModel. In another context I'd like to convert a NullableDecimal into a String in the same way... Is it possible to simply use the existing NullableDecimalToStringConverter inverted? One method is to use the parameter of the converter to tell the converter which way it should convert. But is there a .NET build in way to do such a thing? Another way would be to build a base class with both conversion methods and two separate converter which call the base class methods...

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  • Spring MVC simple case

    - by coure2011
    Trying to understand a sample code... I am returning a modelview successfully from my AthuenticationController like this modelAndView = new ModelAndView("redirect:/home/"); .... return modelAndView; and my browser url is changed to /home/ but its showing a 404 page I have a HomePageController and it has methods @RequestMapping(method = RequestMethod.GET) public String loadHome and @RequestMapping(method = RequestMethod.GET, value = "/main") public String reloadHome but System.out.println("Message") is not executing in any of the above methods. When authenticated I want to load a home.jsp page? It is in WEB-INF/jsp/...

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  • Is there a way to determine gaps in try/catch coverage?

    - by Mike Pateras
    I'm debugging a service that's experiencing some problems on start-up. To aid me in this, I'm wrapping pretty much everything in a try/catch block, and writing any errors to a file. I don't want to put them in every method, I just want to put them in the highest level methods so that they catch exceptions from other methods. Something is getting through, though, as the service does stop under some conditions. Is there a way to determine where the gaps in my try/catch coverage are, other than by sight?

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  • organizing unit test

    - by soulmerge
    I have found several conventions to housekeeping unit tests in a project and I'm not sure which approach would be suitable for our next PHP project. I am trying to find the best convention to encourage easy development and accessibility of the tests when reviewing the source code. I would be very interested in your experience/opinion regarding each: One folder for productive code, another for unit tests: This separates unit tests from the logic files of the project. This separation of concerns is as much a nuisance as it is an advantage: Someone looking into the source code of the project will - so I suppose - either browse the implementation or the unit tests (or more commonly: the implementation only). The advantage of unit tests being another viewpoint to your classes is lost - those two viewpoints are just too far apart IMO. Annotated test methods: Any modern unit testing framework I know allows developers to create dedicated test methods, annotating them (@test) and embedding them in the project code. The big drawback I see here is that the project files get cluttered. Even if these methods are separated using a comment header (like UNIT TESTS below this line) it just bloats the class unnecessarily. Test files within the same folders as the implementation files: Our file naming convention dictates that PHP files containing classes (one class per file) should end with .class.php. I could imagine that putting unit tests regarding a class file into another one ending on .test.php would render the tests much more present to other developers without tainting the class. Although it bloats the project folders, instead of the implementation files, this is my favorite so far, but I have my doubts: I would think others have come up with this already, and discarded this option for some reason (i.e. I have not seen a java project with the files Foo.java and FooTest.java within the same folder.) Maybe it's because java developers make heavier use of IDEs that allow them easier access to the tests, whereas in PHP no big editors have emerged (like eclipse for java) - many devs I know use vim/emacs or similar editors with little support for PHP development per se. What is your experience with any of these unit test placements? Do you have another convention I haven't listed here? Or am I just overrating unit test accessibility to reviewing developers?

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