Question

I’m trying to understand when it is required to declare a function in a header file when inheriting methods from a parent class.

For example lets say I have the following class:

class parent{
public:
    virtual void foo()= 0;
}

Lets say I have a child class that inherits from parent do I have to also declare foo in child’s header file or can I simply define the method in the source file for child?

Would the following delaration be incorrect?

Headerfile:

class child : public parent{
}

Classfile:

child::foo(){
// do something
}

Answer 1

You do not have to declare foo() in the child’s class definition or its header. It is inherited automatically – that’s what inheritance means. (Of course, the function would have to be public rather than private in the base class (parent), but that’s a minor peccadillo.)

You simply define the method in the source file for the child class.