While we can inherit from base class/interface, why can’t we declare a List<> using same class/interface? interface A { } class B : A { } class C : B { } class Test { static void Main(string[] args) { A a = new C(); // OK List<A> listOfA = new List<C>(); // compiler Error … Read more
I get some error that I can’t figure out. Any clue what is wrong with my sample code? class B: def meth(self, arg): print arg class C(B): def meth(self, arg): super(C, self).meth(arg) print C().meth(1) I got the sample test code from help of ‘super’ built-in method. Here is the error: Traceback (most recent call last): … Read more
In JavaScript, every object is at the same time an instance and a class. To do inheritance, you can use any object instance as a prototype. In Python, C++, etc.. there are classes, and instances, as separate concepts. In order to do inheritance, you have to use the base class to create a new class, … Read more
I have two projects: Parent project: A, Sub project: B A/pom.xml: <groupId>com.dummy.bla</groupId> <artifactId>parent</artifactId> <version>0.1-SNAPSHOT</version> <packaging>pom</packaging> And in B/pom.xml, I have: <parent> <groupId>com.dummy.bla</groupId> <artifactId>parent</artifactId> <version>0.1-SNAPSHOT</version> </parent> <groupId>com.dummy.bla.sub</groupId> <artifactId>kid</artifactId> I want B to inherit the version from parent, so the only place in my case I need to put 0.1-SNAPSHOT is A/pom.xml. But if i remove the … Read more
I have several classes that do not really need any state. From the organizational point of view, I would like to put them into hierarchy. But it seems I can’t declare inheritance for static classes. Something like that: public static class Base { } public static class Inherited : Base { } will not work. … Read more
If the classes below were not templates I could simply have x in the derived class. However, with the code below, I have to use this->x. Why? template <typename T> class base { protected: int x; }; template <typename T> class derived : public base<T> { public: int f() { return this->x; } }; int … Read more
Are Composition and Inheritance the same? If I want to implement the composition pattern, how can I do that in Java? 17 Answers 17
I don’t understand why there is no inheritance in Java annotations, just as Java classes. I think it would be very useful. For example: I want to know if a given annotation is a validator. With inheritance, I could reflexively navigate through superclasses to know if this annotation extends a ValidatorAnnotation. Otherwise, how can I … Read more
How can I make as “perfect” a subclass of dict as possible? The end goal is to have a simple dict in which the keys are lowercase. It would seem that there should be some tiny set of primitives I can override to make this work, but according to all my research and attempts it … Read more
Wondering what the difference is between the following: Case 1: Base Class public void DoIt(); Case 1: Inherited class public new void DoIt(); Case 2: Base Class public virtual void DoIt(); Case 2: Inherited class public override void DoIt(); Both case 1 and 2 appear to have the same effect based on the tests I … Read more
