abstract

I feel like I skipped a C# class or two, but here's my dilemma: I have an abstract class from which I derive multiple child classes. I know for sure that for each of the child classes I will have a constructor that needs a certain static object as a model and this object will be different for each of the child classes. My first approach was to make a public static object in the abstract parent class and then, before I start creating any instances of the child classes, I would modify it for each of them, but it turns out that this way I actually make only ONE static object, for the abstract

I understand that Perl's OO model is rather primitive; it is, in most respects, essentially a namespace hack. Nevertheless, I wonder if it is possible to create something like an "interface?" My goal is to have a base class from which others are extended whose principal purpose is to make mandatory the implementation of certain methods (by name is fine, no signature necessary) by those subclasses. I don't really care if it's a "purely virtual" class (like an "interface" in Java) or a concrete class with actual implementational stubs for those methods in the superclass, but what I want is to

I know it can be done in Java, as I have used this technique quite extensively in the past. An example in Java would be shown below. (Additional question. What is this technique called? It's hard to find an example of this without a name.) public abstract class Example { public abstract void doStuff(); } public class StartHere{ public static void main(string[] args){ Example x = new Example(){ public void doStuff(){ System.out.println("Did stuff"); } }; x.doStuff(); } } Now, my main question would be, can this also be done in C#, and if so, how? With lamba expressions and class initializers

I noticed that you can't have abstract constants in PHP. Is there a way I can force a child class to define a constant (which I need to use in one of the abstract class internal methods) ? Baba A constant is a constant ; there is no abstract or private constants in PHP as far as I know, but you can have a work around: Sample Abstract Class abstract class Hello { const CONSTANT_1 = 'abstract'; // Make Abstract const CONSTANT_2 = 'abstract'; // Make Abstract const CONSTANT_3 = 'Hello World'; // Normal Constant function __construct() { Enforcer::__add(__CLASS__, get_called_class()); } } This

I just start out with an example, that explains it best: public abstract class A{ static String str; } public class B extends A{ public B(){ str = "123"; } } public class C extends A{ public C(){ str = "abc"; } } public class Main{ public static void main(String[] args){ A b = new B(); A c = new C(); System.out.println("b.str = " + b.str); System.out.println("c.str = " + c.str); } } This will print out: b.str = abc c.str = abc But I would like a solution where each subclass that instantiate the super class, has their own class variable, at the same time I want to be able to reference that

As we all know, some languages have the notion of interfaces. This is Java: public interface Testable { void test(); } How can I achieve this in C++ (or C++11) in most compact way and with little code noise? I'd appreciate a solution that wouldn't need a separate definition (let the header be sufficient). This is a very simple approach that even I find buggy ;-) class Testable { public: virtual void test() = 0; protected: Testable(); Testable(const Testable& that); Testable& operator= (const Testable& that); virtual ~Testable(); } This is only the beginning.. and already longer that I'd want.

I was going over the official Oracle tutorial where it introduces the idea of polymorphism with the example of a class hierarchy of 3 classes; Bicycle being the superclass, and MountainBike and RoadBike being 2 subclasses. It shows how the 2 subclasses override a method "printDescription" declared in Bicycle, by declaring different versions of it. And finally, toward the end, the tutorial mentions the Java Virtual Machine (JVM) calls the appropriate method for the object that is referred to in each variable. But, nowhere does the tutorial on polymorphism mention the concept of "abstract"