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  • Weird use of generics

    - by Karl Trumstedt
    After a bit of programming one of my classes used generics in a way I never seen before. I would like some opinions of this, if it's bad coding or not. abstract class Base<T> : where T : Base<T> { // omitted methods and properties. virtual void CopyTo(T instance) { /*code*/ } } class Derived : Base<Derived> { override void CopyTo(Derived instance) { base.CopyTo(instance); // copy remaining stuff here } } is this an OK use of generics or not? I'm mostly thinking about the constraint to "itself". I sometimes feel like generics can "explode" to other classes where I use the Base class.

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  • What's the reason both Image and Bitmap classes don't implement a custom equality/hashcode logic?

    - by devoured elysium
    From MSDN documentation, it seems as both GetHashCode() and Equals() haven't been overriden in Bitmap. Neither have them been overriden in Image. So both classes are using the Object's version of them just compares references. I wasn't too convinced so I decided to fire up Reflector to check it out. It seems MSDN is correct in that matter. So, is there any special reason why MS guys wouldn't implement "comparison logic", at least for the Bitmap class? I find it is kinda acceptable for Image, as it is an abstract class, but not so much for the Bitmap class. I can see in a lot of situations calculating the hash code can be an expensive operation, but it'd be alright if it used some kind of lazy evaluation (storing the computed hash code integer in a variable a variable, so it wouldn't have to calculate it later again). When wanting to compare 2 bitmaps, will I have to resort to having to run all over the picture comparing each one of its pixels? Thanks

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  • [C++]Advantage of using a static member function instead of an equivalent non-static member function

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • GetProperties() to return all properties for an interface inheritance hierarchy

    - by sduplooy
    Assuming the following hypothetical inheritance hierarchy: public interface IA { int ID { get; set; } } public interface IB : IA { string Name { get; set; } } Using reflection and making the following call: typeof(IB).GetProperties(BindingFlags.Public | BindingFlags.Instance) will only yield the properties of interface IB, which is "Name". If we were to do a similar test on the following code, public abstract class A { public int ID { get; set; } } public class B : A { public string Name { get; set; } } the call typeof(B).GetProperties(BindingFlags.Public | BindingFlags.Instance) will return an array of PropertyInfo objects for "ID" and "Name". Is there an easy way to find all the properties in the inheritance hierarchy for interfaces as in the first example?

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  • EntityManager and two DAO with PersistenceContextType.EXTENDED

    - by hsd
    Hi All, I have a problem with my entity manager in my application. I have two DAO clasess like this: @Repository public abstract class DaoA { protected ClassA persistentClass; @PersistenceContext(name="my.persistence", type=PersistenceContextType.EXTENDED) protected EntityManager entityManager; -------------- some typical action for DAO -------------- } Second DAO is for ClassB and looks similar to DaoA. The rest of things are done for me by the Spring framework. When I'm debugging the application I recognize that both DAO objects have different instances of EntityManager. In the result my two different DAOs are connected with different PersistenceContext. Question is if this is correct behaviour or not? I would like to have the same PersistenceContext for all my DAO classes. Please give me a hint if this is possible and if I understood the JPA correctly? Regards Hsd

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  • PHP: prevent invocation of method X from from context != Y

    - by sunwukung
    This is a tricky one. I am "emulating" ZF Bootstrapping (surface appearance). Don't ask me why, call it academic interest. So I have a Bootstrap Abstract with a method "run" that iterates over itself to locate any methods prefixed with "init". The application looks for a user defined class which extends this class, in which the user can define any number of methods in this way. However, I want to prevent the user from being able to execute the "run" command of it's parent class, while still exposing the same command for the client code. Anyone got any thoughts/advice/guidance? regards SWK

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  • extend web server to serve static files

    - by Turtle
    Hello, I want to extend a web server which is only able to handle RPC handling now. The web server is written in C#. It provides a abstract handler function like following: public string owsHandler(string request, string path, string param, OSHttpRequest httpRequest, OSHttpResponse httpResponse) And I wrote following code to handle image files: Bitmap queryImg = new Bitmap(path); System.IO.MemoryStream stream = new System.IO.MemoryStream(); queryImg.Save(stream, System.Drawing.Imaging.ImageFormat.Bmp); queryImg.Dispose(); byte[] byteImage = stream.ToArray(); stream.Dispose(); return Convert.ToBase64String(byteImage); And I test it in the browser, the image is returned but the image dimension info is missed. Shall I add something more to the code? Or is any general way to server static files? I do not want to serve it in a ASP.net server. Thanks

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  • Rails - building an absolute url in a model's virtual attribute without url helper

    - by Nick
    I have a model that has paperclip attachments. The model might be used in multiple rails apps I need to return a full (non-relative) url to the attachment as part of a JSON API being consumed elsewhere. I'd like to abstract the paperclip aspect and have a simple virtual attribute like this: def thumbnail_url self.photo.url(:thumb) end This however only gives me the relative path. Since it's in the model I can't use the URL helper methods, right? What would be a good approach to prepending the application root url since I don't have helper support? I would like to avoid hardcoding something or adding code to the controller method that assembles my JSON. Thank you

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  • Code doesn't work in foreach

    - by Arlen Beiler
    Here is my code: var divarray = document.getElementById("yui-main").getElementsByTagName("div"); var articleHTML; var absHTML; var keyHTML; var bodyHTML = []; for( var i in divarray) { if(divarray[i].className == "articleBody"){ articleHTML = divarray[i]; for( var j in articleHTML ){ bodyHTML[i] = ''; if(articleHTML[j].className == "issueMiniFeature"){continue;} if(articleHTML[j].className == "abstract"){absHTML = articleHTML[i]; continue;} if(articleHTML[j].className == "journalKeywords"){keyHTML = articleHTML[i]; continue;} bodyHTML[i] = articleHTML[i]; } break; } i++; } The error I am getting is: SyntaxError: Unexpected token var I am using Google Chrome

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  • Fastest method for SQL Server inserts, updates, selects

    - by Ian
    I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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  • How to achieve table like rows within container using CSS

    - by Barry
    I'm helping an artist maintain her website and have inherited some pretty outdated code. Have moved lots of redundant common code to include files and am now working on moving from inline styles to more CSS-driven styles. For the gallery pages, e.g. http://artistsatlaketahoe.com/abstract.html, a lot of inline styling is used to force the current layout. My preference would be to replace this entirely with CSS that presents the following table-like layout within the "content" div: [image] [image descriptives and purchase button] [image] [image descriptives and purchase button] [image] [image descriptives and purchase button] I'd like to middle-align the image descriptives & purchase button relative to the image if possible. And then apply some padding above and below each row to stop using tags for vertical spacing. Any ideas how to create a div that I can use to get this kind of layout? Thanks!

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  • Nested class with hidden constructor impossible in c#?

    - by luckyluke
    I' ve been doing some programming lately and faced an issue which i found weird in c#. (at least for me) public class Foo { //whatever public class FooSpecificCollection : List<Bar> { //implementation details } public FooSpecificCollection GetFoosStuff() { //return the collection } } I want the consumer of Foo to be able to obtain a reference to FooSpecificCollection, even perform some operations on it. Maybe even set it to some other property of Foo or smth like that, but not To be able to CREATE an instance of this class. (the only class that should be able to instatiate this collection should be Foo. Is my request really that far-fetched? I know that people way smarter defined c# but shouldn't there be such an option that a parent class can create a nested class instance but nobody else can't. So far I created a solution to make an abstract class, or interface available through the property and implement a concrete private class that is not available anywhere else. Is this a correct way to handle such a situation.?

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  • Is it possible to create a domain model for legacy code without refactoring?

    - by plaureano
    I currently have a client that wants me to 'abstract' out a domain model from the existing code but they specifically said that I shouldn't refactor the existing code itself. My question is 1) whether or not this is advisable and 2) what techniques would you apply in this scenario if you can't refactor the code yet they expect you to come up with a model for it? (EDIT: I can't quite put my finger on it, but somehow, not being able to refactor in this case just feels wrong. Has anyone else run into this type of scenario?)

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  • How to declare a generic constraint that is a generic type

    - by HackedByChinese
    I have a two generic abstract types: Entity and Association. Let's say Entity looks like this: public class Entity<TId> { //... } and Association looks like this: public class Association<TEntity, TEntity2> { //... } How do I constrain Association so they can be of any Entity? I can accomplish it by the following: public class Association<TEntity, TId, TEntity2, TId2> where TEntity : Entity<TId> where TEntity2: Entity<TId2> { //... } This gets very tedious as more types derive from Association, because I have to keep passing down TId and TId2. Is there a simpler way to do this, besides just removing the constraint?

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  • Fastest method for SQL Server inserts, updates, selects from C# ASP.Net 2.0+

    - by Ian
    Hi All, long time listener, first time caller. I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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  • Use delegate for Projection in Linq to SQL

    - by Redeemed1
    I have code something like this in an IRepository implementation in Linq to Sql: var newlist = from h in list where h.StringProp1 == "1" select new MyBusinessBO{ firstProp = h.StringProp1, secondProp = h.StringProp2 }; The projection into MyBusinessBO is not difificult but when the Business Object has many properties the projection code becomes very lengthy. Also, as the projection can occur in several places in the Repository we break the DRY principle. Is there any way to abstract out the projection or replace it with a delegate? I.e. replace the code firstProp = h.StringProp1, secondProp = h.StringProp2 with something reusable?

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  • creative way for implementing Data object with it's corespanding buisness logic class in java

    - by ekeren
    I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity reasons lets call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I loose my hierarchy freedom, does any of you have any creative solution for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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  • Vendor neutral SQL

    - by Sparafusile
    I'm currently working on a project for a web application that may be installed on several different servers with various software configurations. I want to make my application as flexible as possible by allowing the user to have various SQL servers installed. The problem is the SQL syntax used by any two server vendors does not match up. For a simple example, here is the same SELECT statement for MS SQL and MySQL: MS SQL - SELECT TOP 1 * FROM MyTable ORDER BY DateCreated DESC MySQL - SELECT * FROM MyTable ORDER BY DateCreated DESC LIMIT 1 Are there any standard way to abstract the statement creation for various vendors? Any online resources or books discussing this problem? Any hints or smart-alec remarks that I'd find useful? Further information: I'm writing my we application in vanilla ASP running on a Windows server. Thanks, Spara

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  • Learning C++ from scratch in Visual Studio?

    - by flesh
    I need to get up to speed with C++ quite quickly (I've never used it previously) - is learning through Visual Studio (i.e. Managed C++) going to be any use? Or will I end up learning the extensions and idiosyncracies of C++ in VS, rather then the language itself? If learning in VS is not recommended, what platform / IDE do you guys suggest? Edit: Can anyone elaborate on what VS will hide or manage for me when coding unmanaged C++? I really need to be learning things like pointers, garbage collection and all the nuts and bolts of the low level language.. does VS abstract or hide any of this kind of stuff from you? Thanks for all the suggestions..

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  • Static nested class visibility issue with Scala / Java interop

    - by Matt R
    Suppose I have the following Java file in a library: package test; public abstract class AbstractFoo { protected static class FooHelper { public FooHelper() {} } } I would like to extend it from Scala: package test2 import test.AbstractFoo class Foo extends AbstractFoo { new AbstractFoo.FooHelper() } I get an error, "class FooHelper cannot be accessed in object test.AbstractFoo". (I'm using a Scala 2.8 nightly). The following Java compiles correctly: package test2; import test.AbstractFoo; public class Foo2 extends AbstractFoo { { new FooHelper(); } } The Scala version also compiles if it's placed in the test package. Is there another way to get it to compile?

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  • How to handle JPA annotations for a pointer to a generic interface

    - by HDave
    I have a generic class that is also a mapped super class that has a private field that holds a pointer to another object of the same type: @MappedSuperclass public abstract class MyClass<T extends MyIfc<T>> implements MyIfc<T> { @OneToOne() @JoinColumn(name = "previous", nullable = true) private T previous; ... } My problem is that Eclipse is showing an error in the file at the OneToOne "Target Entity "T" for previous is not an Entity." All of the implementations of MyIfc are, in fact, Entities. I should also add that each concrete implementation that inherit from MyClass uses a different value for T (because T is itself) so I can't use the "targetEntity" attribute. I guess if there is no answer then I'll have to move this JPA annotation to all the concrete subclasses of MyClass. It just seems like JPA/Hibernate should be smart enough to know it'll all work out at run-time. Makes me wonder if I should just ignore this error somehow.

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  • Lackadaisical One-to-One between Char and Byte Streams

    - by Vaibhav Bajpai
    I expected to have a one-to-one correspondence between the character streams and byte streams in terms of how the classes are organized in their hierarchy. FilterReader and FilterWriter (character streams) correspond back to FilterInputStream and FilterOutputStream (byte stream) classes. However I noticed few changes as - BufferedInputStream extends FilterInputStream, but BufferedReader does NOT extend FilterReader. BufferedOutputStream and PrintStream both extend FilterOutputStream, but BufferedWriter and PrintWriter does NOT extend FilterWriter. FilterInputStream and FilterOutputStream are not abstract classes, but FilterReader and FilterWriter are. I am not sure if I am being too paranoid to point out such differences, but was just curious to know if there was design reasoning behind such decision.

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  • Extract Generic types from extended Generic

    - by Brigham
    I'm trying to refactor a class and set of subclasses where the M type does extend anything, even though we know it has to be a subclass of a certain type. That type is parametrized and I would like its parametrized types to be available to subclasses that already have values for M. Is there any way to define this class without having to include the redundant K and V generic types in the parameter list. I'd like to be able to have the compiler infer them from whatever M is mapped to by subclasses. public abstract class NewParametrized<K, V, M extends SomeParametrized<K, V>> { public void someMethodThatTakesKAndV(K k1, V v1) { } } In other words, I'd like the class declaration to look something like: public class NewParametrized<M extends SomeParametrized<K, V>> { And K and V's types would be inferred from the definition of M.

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  • Java: Stopping a thread that has run for too long?

    - by Thomas King
    Say I've got something like this public void run(){ Thread behaviourThread = new Thread(abstractBehaviours[i]); behaviourThread.start(); } And I want to wait until abstractBehaviours[i] run method has either finished or run for 5000 milliseconds. How do I do that? behaviourThread.join(5000) doesn't seem to do that afaik (something is wrong with my code and I've put it down to that). All the abstract abstractBehaviour class is of course Runnable. I don't want to implement it inside each run method as that seems ugly and there are many different behaviours, I'd much rather have it in the calling/executing thread and do it just once. Solutions? First time doing something as threaded as this. Thanks!

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  • VS compiling Error 1256 ( integer overflow in internal computation ... ) during inheritance

    - by odbb
    Hi there, my problem occurs during compiling Irrlicht3D Engine in VS 2008. 1Error 1256: integer overflow in internal computation due to size or complexity of "irr::IReferenceCounted" I'm currently merging a very old Softwaredriver I have written with the rest of the engine which is much newer. The main Problme is that I have tried to resolve abstract inherince problems. But now I get this error and it is the only one. "irr::IReferenceCounted" is one of the base classes used by other classes which have been inherinced from. What does that mean? I know that an integer overflow can be a normal overflow, but why is this shown during compilation? Any help appreciated! -db

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