问题
The title is probably confusing.
Suppose we have the following set up;
class A
{
public:
virtual void fn() = 0;
};
class B
{
public:
virtual int fn() {};
};
class C: public A, public B
{
};
Is there any way to define A::fn in class C?
回答1:
No. This is not possible. It will always conflict with either of the fn().
The syntax of fn() are different,
void fn(); // in A
and in B is,
int fn(); // in B
You have to make those syntax same in A and B to let C implement the fn(). Demo.
回答2:
There's no way in C to specify that one of the C::fn()
implementations overloads A::fn() (and presumably another overloads
B::fn()). What you can do, however, is introduce an intermediate
class which “renames” the functions, something like:
class RemapA : public A
{
virtual void fnInA() = 0;
public:
virtual void fn()
{
fnInA();
}
};
class RemapB : public B
{
virtual int fnInB() = 0;
public:
virtual int fn()
{
return fnInB();
}
};
class C : public RemapA, public RemapB
{
virtual void fnInA() { /* ... */ }
virtual void fnInB() { /* ... */ }
// ...
};
回答3:
You might want to read my answer to the following question: Implement two functions with the same name but different, non-covariant return types due to multiple abstract base classes In short: Yes, with some restrictions on calling it. It can be called as an A (pointer or reference) or a B (pointer or reference), but not as a C, as that would be ambiguous.
来源：https://stackoverflow.com/questions/7319494/overloading-virtual-functions-of-the-same-name-from-different-base-classes-is-i