C++ Inheritance: Calling Base Class Constructor In Header

Question

Assume class Child is a derived class of the class Parent. In a five file program, how would I specify in Child.h that I want to call the constructor of Parent? I don't think something like the following is legal inside the header:

Child(int Param, int ParamTwo) : Parent(Param);

In this situation, what should Child.cpp's constructor syntax look like?

Solution 1

In Child.h, you would simply declare:

Child(int Param, int ParamTwo);

In Child.cpp, you would then have:

Child::Child(int Param, int ParamTwo) : Parent(Param) {
    //rest of constructor here
}

Solution 2

The initialization list of a constructor is part of its definition. You can either define it inline in your class declaration

class Child : public Parent {
    // ...
    Child(int Param, int ParamTwo) : Parent(Param)
    { /* Note the body */ }
};

or just declare it

class Child : public Parent {
    // ...
    Child(int Param, int ParamTwo);
};

and define in the compilation unit (Child.cpp)

Child::Child(int Param, int ParamTwo) : Parent(Param) {
}

Comments

[Wolf]

+1 BTW: using implementation instead of definition could be less misleading.

[Vinz]

What if I don't have a .cpp file and it's something like an interface?