c++ Multiple parents with same variable name

问题

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.

回答1:

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.

回答2:

You can access them in class C by A::var and B::var respectively.

Here is a link that covers the same problem.

回答3:

If you only refer to var inside of C, the compiler does not know whether you mean A::var or B::var and the compiler will tell you that var is ambiguous. Therefore, you have to fully qualify the name when using var.

No merging happens, any instance of C will contain both variables.

来源：https://stackoverflow.com/questions/12255087/c-multiple-parents-with-same-variable-name