CODEWITHSUNDEEP
c++overloading
cb7
cb7

Reputation: 523

Understanding which method will be invoked

A class Base has a method void foo(float a). Class Sub inherits publicly from Base and has a method void foo(int a).

I have s an instance of Sub (stored in a Sub*), and call s->foo(1.5). It's Sub::foo that gets executed (with the argument truncated to 1), rather than Base::foo. Why is this?

I would naively expect it to execute the original method defined in Base, seeing as the argument is a float. How could I achieve this instead?

Upvotes: 0

Views: 73

Answers (1)

Jarod42
Jarod42

Reputation: 218268

With

struct Base
{
    void foo(float a);
};

struct Sub : Base
{
    void foo(int a); // Hides Base::Foo
};

Sub::foo hides Base::foo,

you have to add using to allow both overloads.

struct Sub : Base
{
    using Base::foo;
    void foo(int a);
};

More details on using_declaration

And for your call:

Sub s;
s.foo(1.5); // Ambiguous with using, Sub::foo(int) without using.

without using, only one overload is considered, so Sub::foo(int) is called.

With using, both overloads are considered, but neither is a better match than the other, so it is ambiguous.

Upvotes: 4

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