multiple-inheritance

I have two questions converning metaclasses and multiple inheritance. The first is: Why do I get a TypeError for the class Derived but not for Derived2 ? class Metaclass(type): pass class Klass(object): __metaclass__ = Metaclass #class Derived(object, Klass): pass # if I uncomment this, I get a TypeError class OtherClass(object): pass class Derived2(OtherClass, Klass): pass # I do not get a TypeError for this The exact error message is: TypeError: Error when calling the metaclass bases Cannot create a consistent method resolution order (MRO) for bases object, Klass The second question is: Why

I got some warnings by using pure virtual interfaces on some MFC CWnd derived objects through multiple inheritance. I believe it's caused by defining the methods which need to be implemented for the message map. warning C4407: cast between different pointer to member representations, compiler may generate incorrect code That sounds like a bit more than a warning, more like something that might cause heap corruption. So is there another way to do something similar to below that won't cause the MFC dynamic downcast macros to choke anymore than usual? class ISomeInterface { public: virtual

Okay, sample code first; this is my attempt at communicating what it is that I'm trying to do, although it doesn't compile: #include <iostream> template <class T> class Base { public: virtual void my_callback() = 0; }; class Derived1 : public Base<int> , public Base<float> { public: void my_callback<int>() { cout << "Int callback for Derived1.\n"; } void my_callback<float>() { cout << "Float callback for Derived\n"; } }; class Derived2 : public Base<int> , public Base<float> { public: void my_callback<int>() { cout << "Int callback for Derived2.\n"; } void my_callback<float>() { cout << "Float

I know this might be crazy but today one of my friend puzzled by asking when we implement an interface in java is it considered as method overriding. I told him it is not overriding as we are providing working(definition) of method first time when we implement any interface. To support multiple inheritance java provide interface but he was not convinced and was arguing. Please bring some light on to the topic. The term "overriding" applies when there is an existing implementation of the method . The correct term is "implementing" for interfaces and other abstract declarations. The @Override

I have declared two service contracts as follows: [ServiceContract] public interface IContract1 { [OperationContract] double Add(int ip); } [ServiceContract] public interface IContract2 { [OperationContract] double Add(double ip); } I have a class which implements these two contracts. I have created two endpoints for both contracts. But I'm not able to access the service from client code. It displays a big error when I try to update the service reference as: Metadata contains an error that cannot be resolved.... There was no endpoint listening at ... , etc. I know that you can't have two

What I am looking to do is develop two different base classes which should not be inherited together in the one derived class. Is there any way I can enforce this at compile time? class Base1 {}; class Base2 {}; class Derived1 : public Base1 {} // OK! class Derived2 : public Base2, public Other {} // OK! class Derived3 : public Base1, Base2 {} // Can I force the compiler to complain? Derived1 d1; // OK! Derived2 d2; // OK! Derived3 d3; // Or can I force the compiler to complain here? I'm aware that documentation is a good idea, just wondering if it is possible. You are setting up some kind of

class A{ protected: int var; }; class B{ protected: int var; }; class C : public A, public B {}; What happens here? Do the variable merges? Can I call one in specific like, B::var = 2, etc. You class C will have two variables, B::var and A::var . Outside of C you can access them like this (if you change to public: ), C c; c.A::var = 2; Attempting to access c.var will lead to an error, since there is no field with the name var , only A::var and B::var . Inside C they behave like regular fields, again, with the names A::var and B::var . You can access them in class C by A::var and B::var

I have diamond hierarchy of classes: A / \ B C \ / D To avoid two copies of A in D, we need to use virtual inheritance at B and C. class A { }; class B: virtual public A {}; class C: virtual public A { }; class D: public B, public C { }; Question: Why does virtual inheritance needs to be performed at B and C, even though the ambiguity is at D? It would have been more intuitive if it is at D. Why is this feature designed like this by standards committee? What can we do if B and C classes are coming from 3rd party library ? EDIT: My answer was to indicate B and C classes that they should not