Access child member methods from function taking parent class

Question

A test function needs to take in any object of a class that is derived from Parent and access the Child implementation of Function(). To me, this would seem like something easy to do. I tried to do the following. it feels intuitively right, but it does not work. It still calls the Parent implementation of Function()

Class Parent
{
Public:
    Parent();
    ~Parent();

    virtual void Function() = 0;

};

Class Child : public Parent
{
Public:
    Child();
    ~Child();
    void Function(){
        // Do something
    };
};

void Test(Parent Object)
{
    Object.Function();
};

int main()
{
    Child Object;
    Test(Child);
    return 0;
}

How would one implement such a thing?

Am I missing something small? or is this solution far off what I am trying to achieve?

Thanks in advance.

`Parent.Function();` should be `object.Function();` and the same with the Child object. note that you are passing a copy of the Child object and it will be sliced. the polymorphic behavior can be demonstrated by pointers not by ordinary objects. — asmmo, Mar 22 '20 at 11:05
Sorry but have you tried to compile the code as shown. It's important that the code you provide is, as I said, the *real* code. — G.M., Mar 22 '20 at 11:16

john · Accepted Answer · 2020-03-22T12:56:12.773

2

To use virtual functions in C++ you must use a reference or a pointer. Try this

void Test(Parent& Object) // reference to Parent
{
    Object.Function();
};

You should research object slicing to understand what goes wrong with your version, and why you must use a reference or a pointer.

edited Mar 22 '20 at 12:56

answered Mar 22 '20 at 10:55

john

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A typo: `Object.Function()` – theWiseBro Mar 22 '20 at 11:03

Access child member methods from function taking parent class

1 Answers1