inheritance

问题 When I call a method that was overrided from my constructor, I am getting an error and it says that it is missing an argument (due to the subclass requiring a second argument). However, I called the method in the super(), so why doesn't it call the super class version of that method? This is best illustrated with a short example: class A: def __init__(self): self.do() def do(self): print("A") class B(A): def __init__(self): super().__init__() self.do("B") def do(self, arg2): super().do()

问题 What is the order of constructor call in virtual inheritance in c++? For the following two cases of multiple inheritance; (I) for the following code, without virtual inheritance; class a { public: a() { cout<<"\t a"; } }; class b: public a { public: b() { cout<<"\t b"; } }; class c: public b { public: c() { cout<<"\t c"; } }; class d: public c { public: d() { cout<<"\t d"; } }; class e: public c, public d { public: e() { cout<<"\t e"; } }; class f: public b, public e { public: f() { cout<<"\t

问题 I need to inherit a collection of items of the current type, like this class A { // some properties... public ICollection<A> Children; } class B: A { // other properties } This mostly works as expected. The problem is I can do something like this class C: A { } B b = new B(); b.Children = new List<C>(); Is there any way to force b.Children to be a collection of B ? 回答1: No, there is no way to do such thing yet. The C# language has no artifact to declare such thing: class A { public

问题 I need to inherit a collection of items of the current type, like this class A { // some properties... public ICollection<A> Children; } class B: A { // other properties } This mostly works as expected. The problem is I can do something like this class C: A { } B b = new B(); b.Children = new List<C>(); Is there any way to force b.Children to be a collection of B ? 回答1: No, there is no way to do such thing yet. The C# language has no artifact to declare such thing: class A { public

问题 I need to inherit a collection of items of the current type, like this class A { // some properties... public ICollection<A> Children; } class B: A { // other properties } This mostly works as expected. The problem is I can do something like this class C: A { } B b = new B(); b.Children = new List<C>(); Is there any way to force b.Children to be a collection of B ? 回答1: No, there is no way to do such thing yet. The C# language has no artifact to declare such thing: class A { public

问题 I'm trying to use AutoMapper (v5.1.1) to map an object which inherits from a List or Collection. The map call does not give me an error but the output is an empty list (of correct type though). I can get a List<DestinationObject> or Collection<DestinationObject> , but it does not seem to work when having a custom class which enherits from List<T> or Collection<T> . I've tried extending the first map definition to include the base class ( List<T> ) but that gives me a StackOverflowException.

问题 Is it possible to change a base class field data type and value in the derived class and still call the base class method but use the derived class values? Sample Code: public class class1 { protected DBContext DB { get; set; } public A() { DB = new DBContext(); } public virtual DBRecord find(int id) { return DB.DBRecord.Find(id); } } public class class2 : class2 { protected DifferentDBContext DB { get; set; } public B() { DB = new DifferentDBContext(); } } And then i tried to call the method

问题 Is it possible to change a base class field data type and value in the derived class and still call the base class method but use the derived class values? Sample Code: public class class1 { protected DBContext DB { get; set; } public A() { DB = new DBContext(); } public virtual DBRecord find(int id) { return DB.DBRecord.Find(id); } } public class class2 : class2 { protected DifferentDBContext DB { get; set; } public B() { DB = new DifferentDBContext(); } } And then i tried to call the method

问题 Is it possible to change a base class field data type and value in the derived class and still call the base class method but use the derived class values? Sample Code: public class class1 { protected DBContext DB { get; set; } public A() { DB = new DBContext(); } public virtual DBRecord find(int id) { return DB.DBRecord.Find(id); } } public class class2 : class2 { protected DifferentDBContext DB { get; set; } public B() { DB = new DifferentDBContext(); } } And then i tried to call the method

问题 I have a class that has to take a custom widget. This one can have two different implementations, so I would like to have an abstract class as interface and create two other classes those extend the abstract one. So, I have: abstract class ICustomWidget extends StatelessWidget{} class A extends ICustomWidget{ @override Widget build(BuildContext context) => //Implementation } class B extends ICustomWidget { @override Widget build(BuildContext context) => //Implementation } I want to ask if