CODEWITHSUNDEEP
c++inheritanceoverloading
Sébastien Bémelmans
Sébastien Bémelmans

Reputation: 910

C++ : Semantic issue on a child class with same named method

This is a question about designing classes in C++.

My base class have virtual final method with parameters, the name of it is basically "update". In a child class, I wanted to use a higher level way to update the object, so I made a method called "update" too (for convenience), but this one have no parameter. And Clang warns me the method is hiding a base class method. In my point of view, I'm not totally agree with this, because the signature is different, it should just complete the overloading.

Is there a good reason to not do that ?

Upvotes: 0

Views: 37

Answers (1)

aschepler
aschepler

Reputation: 72281

The warning is telling you that the function in the derived class makes it more difficult to call the original base class function on an object of the derived type:

class Base {
public:
    virtual void update(int param) final;
};

class Derived : public Base {
public:
    void update();
};

void f(Derived& obj) {
    obj.update(2); // Error!
    // Name lookup for update finds only Derived::update,
    // which takes no arguments
}

To "unhide" the base class function, so that the derived class acts as though it has both overloads, use a using directive:

class Derived : public Base {
public:
    void update();
    using Base::update;
};

Upvotes: 1

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