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• C# Calling Methods in Generic Classes

  - by aip.cd.aish

  I am extending the ImageBox control from EmguCV. The control's Image property can be set to anything implementing the IImage interface. All of the following implement this interface: Image<Bgr, Byte> Image<Ycc, Byte> Image<Hsv, Byte> Now I want to call the Draw method on the object of the above type (what ever it may be). The problem is when I access the Image property, the return type is IImage. IImage does not implement the Draw method, but all of the above do. I believe I can cast the object of type IImage to one of the above (the right one) and I can access the Draw method. But how do I know what the right one is? If you have a better way of doing this, please suggest that as well.

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• Using StructureMap to create classes by a name?

  - by Bevan

  How can I use StructureMap to resolve to an appropriate implementation of an interface based on a name stored in an attribute? In my project, I have many different kinds of widgets, each descending from IWidget, and each decorated with an attribute specifying the kind of associated element. To illustrate: [Configuration("header")] public class HeaderWidget : IWidget { } [Configuration("linegraph")] public class LineGraphWidget : IWidget { } When processing my (XML) configuration file, I want to obtain an instance of the appropriate concrete class based on the name of the element I'm processing. public IWidget CreateWidget(XElement definition) { var kind = definition.Name.LocalName; var widget = // What goes here? widget.Configure(definition); return widget; } Each definition should result in a different widget being created - I don't need or want the instances to be shared. In the past I've written plenty of code to do this kind of thing manually, including writing a custom "roll-your-own" IoC container for one project. However, one of my goals with this project is to become proficient with StructureMap instead of reinventing the wheel. I think I've already managed to set up automatic scanning of assemblies so that StructureMap knows about all my IWidget implementations: public class WidgetRegistration : Registry { public WidgetRegistration() { Scan( scanner => { scanner.AssembliesFromApplicationBaseDirectory(); scanner.AddAllTypesOf<IWidget>(); }); } } However, this isn't registering the names of my widgets with StructureMap. What do I need to add to make my scenario work? (While I am trying to use StructureMap in this project, an answer showing me how to solve this problem with a different DI/IoC tool would still be valuable.)

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• Abstract classes in shared library

  - by JTom

  Hi, I have an ordinary abstract class that has couple of pure virtual methods. The class itself is a part of the shared library. The compilation of the shared library itself is OK. But when the library is linked to another program that has another class deriving from the abstract one in the shared library and defining the pure virtual methods, I get the following linker error: I compile like this..: g++ -I../path/to/the/library main.cpp derived.cpp -L../path/to/the/library -lsomename -o shared ...and the linker error is: libsomename.so: undefined reference to `AbstractClass::method()' It's like the abstract class cannot access its pure virtual methods but I do not try to make any instance of the abstract class anywhere in the library. What could be the problem?

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• NullPointerException when trying to run an applet of multiple classes

  - by Chad

  I'm trying to display an applet in an html page. I've had success doing this in the past, but now that I have more than one class in the applet, I seem to get an error every time I try to load the applet in an html page. For a bit, I was writing the html page by hand, but then I realized the applet viewer in netbeans (the IDE I'm coding in) created an html page for you, which is the same as the one I was coding. The application runs error-free when in the applet viewer, but the following message is displayed when I try to run it in the html page: java.lang.NullPointerException at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source) at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Exception: java.lang.NullPointerException I tested another small, one class applet and it ran fine in the html page under the same conditions. Any ideas what may be wrong?

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• Java: JPA classes, refactoring from Date to DateTime

  - by bguiz

  With a table created using this SQL Create Table X ( ID varchar(4) Not Null, XDATE date ); and an entity class defined like so @Entity @Table(name = "X") public class X implements Serializable { @Id @Basic(optional = false) @Column(name = "ID", nullable = false, length = 4) private String id; @Column(name = "XDATE") @Temporal(TemporalType.DATE) private Date xDate; //java.util.Date ... } With the above, I can use JPA to achieve object relational mapping. However, the xDate attribute can only store dates, e.g. dd/MM/yyyy. How do I refactor the above to store a full date object using just one field, i.e. dd/MM/yyyy HH24:mm?

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• super function doesn't work inside a maya python module

  - by sfjedi

  Somehow, this works fine in the Maya/Python script editor, but fails when it's inside of my module code. Anyone have any ideas? class ControlShape(object): def __init__(self, *args, **kwargs): print 'Inside ControlShape...' class Cross(ControlShape): def __init__(self, *args, **kwargs): print 'Entering Cross...' super(Cross, self).__init__(*args, **kwargs) print 'Leaving Cross...' x = Cross() This gives me a TypeError: super(type, obj): obj must be an instance or subtype of type.

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• How to import your own non-packaged Java classes in Jython

  - by thepandaatemyface

  I know in Jython you can do import java.util.Random as Random Random().nextInt() But if I have a class I wrote myself, how can I import it into Jython without putting the class itself in a package? If I have a testclass Test: public class Test { public void foo() { System.out.println("bar"); } } that's not inside a package. Can I even import that into jython by using something along the lines offrom Test import Test?

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• Why isn't the "this." command needed in this constructor? (java)

  - by David

  I'm reading a book about java. It just got to explaining how you create a class called "deck" which contains an array of cards as its instance variable(s). Here is the code snippit: class Deck { Card[] cards; public Deck (int n) { cards = new Card[n]; } } why isn't the this. command used? for example why isn't the code this: class Deck { Card[[] cards; public Deck (int n) { this.cards = new Card[n]; } }

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• PHP Classes: Call method in instance of a class by instance's name

  - by Ursus Russus

  Hi, i have a class of this kind Class Car { private $color; public function __construct($color){ $this->color=$color; } public function get_color(){ return $this->$color; } } Then i create some instances of it: $blue_car = new car('blue'); $green_car = new car('green'); etc. Now i need to call method get_color() on the fly, according to instance's name $instance_name='green_car'; Is there any way to do it?

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• How to share a variable between two classes?

  - by Altefquatre

  How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it?

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• How to block IP address or IP classes in ASP.NET

  - by FinalDestiny

  I need to block one IP address or class in asp.net Can anyone help me with the code? And how to implement? Thanks

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• is there a rule in CSS that says class="one two" vs class="two one" and the second will override the

  - by Jian Lin

  Right now, there seems to be no such effect. Example: both divs are orange in color on Firefox <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <style> .one { border: 6px dashed green } .two { border: 6px dashed orange } </style> </head> <body> <div class="one two"> hello world </div> <div class="two one"> hello world </div>

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• Twitter Authentication through Android's AccountManager classes.

  - by Robby Pond

  I am working on a twitter based app and am trying to incorporate Android's built-in Account support for Twitter. The following code works to popup the confirmation dialog for my app to access twitter but I am unsure of what to pass in as the authenticationType. Any help would be appreciated. I've googled all over the place and can't seem to find the correct answer. It goes in place of "oauth" below. AccountManager am = AccountManager.get(this); Account[] accts = am.getAccountsByType(TWITTER_ACCOUNT_TYPE); if(accts.length > 0) { Account acct = accts[0]; am.getAuthToken(acct, "oauth"/*what goes here*/, null, this, new AccountManagerCallback<Bundle>() { @Override public void run(AccountManagerFuture<Bundle> arg0) { try { Bundle b = arg0.getResult(); Log.e("TrendDroid", "THIS AUTHTOKEN: " + b.getString(AccountManager.KEY_AUTHTOKEN)); } catch (Exception e) { Log.e("TrendDroid", "EXCEPTION@AUTHTOKEN"); } }}, null); }

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• Declaring variable as PHP class

  - by iamdadude

  I have a variable called $theclass and it's a string "Home_class". How can I define a class out of that string? The reason I need to do this is that the variable will change and I want to be able to declare the class that the variable is equal to. Is this possible? Thanks for any help.

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• SPRING: How do you programmatically instantiate classes based on information passed from Flex UI

  - by babyangel86

  Imagine the UI passes back an XMl node as such: <properties> <type> Source </type> <name> Blooper </name> <delay> <type> Deterministic </type> <parameters> <param> 4 </param> </parameters> <delay> <batch> <type> Erlang </type> <parameters> <param> 4 </param> <param> 6 </param> </parameters> <batch> And behind the scene what it is asking that you instantiate a class as such: new Source("blooper", new Exp(4), new Erlang(4,6); The problem lies in the fact that you don't know what class you will need to processing, and you will be sent a list of these class definitions with instructions on how they can be linked to each other. I've heard that using a BeanFactoryPostProcessor might be helpful, or a property editor/convertor. However I am at a loss as to how best to use them to solve my problem. Any help you can provide will be much appreciated.

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• Wrapper Classes for Backward compatibility in Java

  - by Casebash

  There is an interesting article here on maintaing backwards compatibility for Java. In the wrapper class section, I can't actually understand what the wrapper class accomplishes. In the following code from MyApp, WrapNewClass.checkAvailable() could be replaced by Class.forName("NewClass"). static { try { WrapNewClass.checkAvailable(); mNewClassAvailable = true; } catch (Throwable ex) { mNewClassAvailable = false; } } Consider when NewClass is unavailable. In the code where we use the wrapper (see below), all we have done is replace a class that doesn't exist, with one that exists, but which can't be compiled as it uses a class that doesn't exist. public void diddle() { if (mNewClassAvailable) { WrapNewClass.setGlobalDiv(4); WrapNewClass wnc = new WrapNewClass(40); System.out.println("newer API is available - " + wnc.doStuff(10)); }else { System.out.println("newer API not available"); } } Can anyone explain why this makes a difference? I assume it has something to do with how Java compiles code - which I don't know much about.

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• 2 Classes need each other declared C++

  - by Prodigga

  I have a "Game" class which holds all the games settings and manages the game. I have a "Grid" class which is the grid the game is played on. The "Game" class initializes a "Grid" object as one of its members (passing itself ("this") as one of the parameters for "Grid"s constructor).. The "Grid" object therefor needs to deal with a "Game*" pointer. To do this it needs to know what "Game" is; i need to declare it before "Grid". But "Game" uses "Grid"...so it also needs "Grid" declared before it. so confused on how to include headers/etc correctly here..

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• Java; casting base class to derived class

  - by incrediman

  Why can't I cast a base class instance to a derived class? For example, if I have a class B which extends a class C, why can't I do this? B b=(B)(new C()); or this? C c=new C(); B b=(B)c;

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• Java "this" and inner class

  - by llm

  Is it possible to get a reference to this from within a Java inner class? i.e. Class outer { void aMethod() { NewClass newClass = new NewClass() { void bMethod() { // How to I get access to "this" (pointing to outer) from here? } }; } }

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• How to deserialize implementation classes in OSGi

  - by Daniel Schneller

  In an eRCP OSGi based application the user can push a button and go to a lock screen similar to that of Windows or Mac OS X. When this happens, the current state of the application is serialized to a file and control is handed over to the lock screen. In this mobile application memory is very tight, so we need to get rid of the original view/controller when the lock screen comes up. This works fine and we end up with a binary serialized file. Once the user logs back in, the file is read in again and the original state of the application restored. This works fine as well, except when the controller that was serialized contained a reference to an object which comes from a different bundle. In my concrete case the original controller (from bundle A) can call a web service and gets a result back. Nothing fancy, just some Strings and Numbers in a simple value holder class. However the controller only sees this as a Result interface; the actual runtime object (ResultImpl) is defined and created in a different bundle (bundle B, the webservice client implementation) and returned via a service call. When the deserialization now tries to thaw the controller from the file, it throws a ClassNotFound exception, complaining about not being able to deserialize the result object, because deserialization is called from bundle A, which cannot see the ResultImpl class from bundle B. Any ideas on how to work around that? The only thing I could come up with is to clone all the individual values into another object, defined in the controller's bundle, but this seems like quite a hassle.

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• destructor and copy-constructor calling..(why does it get called at these times)

  - by sil3nt

  Hello there, I have the following code #include <iostream> using namespace std; class Object { public: Object(int id){ cout << "Construct(" << id << ")" << endl; m_id = id; } Object(const Object& obj){ cout << "Copy-construct(" << obj.m_id << ")" << endl; m_id = obj.m_id; } Object& operator=(const Object& obj){ cout << m_id << " = " << obj.m_id << endl; m_id = obj.m_id; return *this; } ~Object(){ cout << "Destruct(" << m_id << ")" << endl; } private: int m_id; }; Object func(Object var) { return var; } int main(){ Object v1(1); cout << "( a )" << endl; Object v2(2); v2 = v1; cout << "( b )" << endl; Object v4 = v1; Object *pv5; pv5 = &v1; pv5 = new Object(5); cout << "( c )" << endl; func(v1); cout << "( d )" << endl; delete pv5; } which outputs Construct(1) ( a ) Construct(2) 2 = 1 ( b ) Copy-construct(1) Construct(5) ( c ) Copy-construct(1) Copy-construct(1) Destruct(1) Destruct(1) ( d ) Destruct(5) Destruct(1) Destruct(1) Destruct(1) I have some issues with this, firstly why does Object v4 = v1; call the copy constructor and produce Copy-construct(1) after the printing of ( b ). Also after the printing of ( c ) the copy-constructor is again called twice?, Im not certain of how this function works to produce that Object func(Object var) { return var; } and just after that Destruct(1) gets called twice before ( d ) is printed. sorry for the long question, I'm confused with the above.

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• Android Proxy Cursor

  - by Alxandr

  I have a database with which I wish to expose data with a ContentProvider. However, it is important that all the colums are not exposed, and also they should be renamed. Is there any good way of doing this? I was thinking maybe some kind of proxy-cursor which takes a cursor and translates its columns to the desired ones, and calls to close and the like would just be replayed to the original cursor. Does something like this exist, or would it be hard to make?

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• How to override inner class methods if the inner class is defined as a property of the top class

  - by Maddy

  I have a code snippet like this class A(object): class b: def print_hello(self): print "Hello world" b = property(b) And I want to override the inner class b (please dont worry about the lowercase name) behaviour. Say, I want to add a new method or I want to change an existing method, like: class C(A): class b(A.b): def print_hello(self): print "Inner Class: Hello world" b = property(b) Now if I create C's object as c = C(), and call c.b I get TypeError: 'property' object is not callable error. How would I get pass this and call print_hello of the extended inner class? Disclaimer: I dont want to change the code for A class.

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• PHP Exceptions in Classes

  - by mike condiff

  I'm writing a web application (PHP) for my friend and have decided to use my limited OOP training from Java. My question is what is the best way to note in my class/application that specific critical things failed without actually breaking my page. Currently my problem is I have an Object "SummerCamper" which takes a camper_id as it's argument to load all of the necessary data into the object from the database. Say someone specifies a camper_id in the querystring that does not exist, I pass it to my objects constructor and the load fails. Currently I don't see a way for me to just return false from the constructor. I have read I could possibly do this with Exceptions, throwing an exception if no records are found in the database or if some sort of validation fails on input of the camper_id from the application etc. However, I have not really found a great way to alert my program that the Object Load has failed. I tried returning false from within the CATCH but the Object still persists in my php page. I do understand I could put a variable $is_valid = false if the load fails and then check the Object using a get method but I think there may be better ways. What is the best way of achieving the essential termination of an object if a load fails? Should I load data into the object from outside the constructor? Is there some osrt of design pattern that I should look into? Any help would be appreciated.

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• Any homologue of InternalsVisibleToAttribute, but for internal classes?

  - by Will Marcouiller

  In my most recent question: Unit Testing Best Practice? / C# InternalsVisibleTo() attribute for VBNET 2.0 while testing?, I was asking about InternalsVisibleToAttribute. I have read the documentation on how to use it, and everything is fine and understood. However, I can't instantiate my class Groupe from my Testing project. I want to be able to instantiate my internal class in my wrapper assembly, from my testing assembly. Any help is appreciated! EDIT Here's the compile-time error I get when I do try to instantiate my type: Erreur 2 'Carra.Exemples.Blocs.ActiveDirectory.Groupe' n'est pas accessible dans ce contexte, car il est 'Private'. C:\Open\Projects\Exemples\Src\Carra.Exemples.Blocs.ActiveDirectory\Carra.Exemples.Blocs.ActiveDirectory.Tests\GroupeTests.vb 9 18 Carra.Exemples.Blocs.ActiveDirectory.Tests (This says that my type is not accessible in this context, because it is private.) But it's Friend (internal)!

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