inheritance

问题 I'm trying to duplicate and then modify a class programmatically but I'm running into problems with python 3's magic super for example the following class Base(): def __init__(self): print("Base init") class Orginal(Base): def __init__(self): super().__init__() print("Orginal init") Modified = type(Orginal.__name__, Orginal.__bases__, dict(Orginal.__dict__)) Modified.f = lambda self: print("f") m = Modified() raises TypeError: super(type, obj): obj must be an instance or subtype of type So I

问题 I want to create a class B that inherits from template class A. And I want the B's nested class E to be the template parameter in this inheritance. More visually: template <class T> class A { } class B : public A<B::E> { class E { int x; } } class C : public A<C::E> { class E { int x; int y; } } I think the problem is that the compiler doesn't know that the class B will have a nested class E by the time it's processing the declaration of B, since I'm getting the error: no member named 'E' in

问题 So I'm reading a book on database design principles and came on the chapter about inheritance, but I'm confused on how I could "connect" sub classes with their super class in MySQL ? The table structure would, for example, look like this So how would I relate these two sub classes with their super class so that I could easily do a query similar to " hey, get me a correct contract type for a Person he is assigned to ". A person could have one of each, or even both of them, if, for example, a

问题 I have 3 level classes. TopClass MiddleClass BottomClass And MiddleClass is derived from TopClass and BottomClass is derived from MiddleClass . I want to have a property in TopClass which could only be accessible from TopClass and MiddleClass not the BottomClass . As I am using protected access modifier, the protected property in TopClass is accessible from BottomClass . Here are my classes to give better insight. public class TopClass { private string ThisIsOnlyAccessibleForTopClass { get;

问题 I'm trying to create a generic to simplify my codes (it's a web api project), but at somehow it's ended up becoming more complicated than I expected. What I'm trying to implement is something like this: To simplify my whole real code, this is what I've written: public interface IDatabaseTable { } public class ReceiptIndex: IDatabaseTable { } public interface IBackend<T> where T: IDatabaseTable { } public class Receipts : IBackend<ReceiptIndex> { } public class Generic<T> : SyncTwoWayXI,

问题 I'm trying to create a generic to simplify my codes (it's a web api project), but at somehow it's ended up becoming more complicated than I expected. What I'm trying to implement is something like this: To simplify my whole real code, this is what I've written: public interface IDatabaseTable { } public class ReceiptIndex: IDatabaseTable { } public interface IBackend<T> where T: IDatabaseTable { } public class Receipts : IBackend<ReceiptIndex> { } public class Generic<T> : SyncTwoWayXI,

问题 I'm trying to create a generic to simplify my codes (it's a web api project), but at somehow it's ended up becoming more complicated than I expected. What I'm trying to implement is something like this: To simplify my whole real code, this is what I've written: public interface IDatabaseTable { } public class ReceiptIndex: IDatabaseTable { } public interface IBackend<T> where T: IDatabaseTable { } public class Receipts : IBackend<ReceiptIndex> { } public class Generic<T> : SyncTwoWayXI,

问题 Consider: Dog is a subclass of Animal , and Dog overrides Animal.eat() Animal[] animals = getAllAnimals(); for (int i = 0; i < animals.length; i++) { animals[i].eat(); } If Animal.eat() is overriden by Dog.eat() , which one is called when the method is called from an identifier of type Animal ( animals[i] ?) 回答1: The subclass method will be called. That's the beauty of polymorphism. 回答2: The subclass will be the only method call, unless the subclass calls the superclass like this: class Dog {

问题 I have a problem with using inherited interface. I will explain my problem on example below. Let's say I have Interface IFlyable : public interface IFlyable { IVerticalSpeed Speed { get; set; } } It contains IVerticalSpeed interface. I created another interface called ISpeed which inherits from IVerticalSpeed interface: public interface ISpeed : IVerticalSpeed { int MaxSpeed { get; set; } } In next step I created a class Fly which implement IFlyable interface: public class Fly : IFlyable {

问题 I have a problem with using inherited interface. I will explain my problem on example below. Let's say I have Interface IFlyable : public interface IFlyable { IVerticalSpeed Speed { get; set; } } It contains IVerticalSpeed interface. I created another interface called ISpeed which inherits from IVerticalSpeed interface: public interface ISpeed : IVerticalSpeed { int MaxSpeed { get; set; } } In next step I created a class Fly which implement IFlyable interface: public class Fly : IFlyable {