how to write C++ inheritance constructors

Question

I've been away from C++ for a while, and I'm having a little trouble with this one. I'll spare you my bad code - can someone please post a 'model answer' for how to write a simple header file and source file for a small class with a constructor that accepts a few values, and passes a few on to it's base classes constructor? I'm worried that I'm making something inline by mistake. Thank you.

Sometimes the simplest answers are the hardest to find clear examples of on the internet.

Answer 1

// ExampleClass.h
#ifndef ExampleClass_H_
#define ExampleClass_H_

#include "ExampleBase.h"

class ExampleClass : public ExampleBase {
public:
    ExampleClass(int a);
};

#endif


// ExampleClass.cpp
#include "ExampleClass.h"

ExampleClass::ExampleClass(int a) : ExampleBase(a)
{
    // other constructor stuff here
}

Answer 2

The initializer list is used to initialize the base classes. Initialize base classes before instance members. Non-virtual base classes are initialized from left to right, so if you have multiple bases, initialize them in the order they are declared.

Here's an example of passing arguments to the base class constructor:

#include <iostream>

struct Base {
    Base(int i) {
        std::cout << i << std::endl;
    }
};

struct Derived : public Base {
    Derived(int i) : Base(i) {}
};

Answer 3

Seeing as the OP requested non-inline versions, I'll repost with modifications.

struct Base {
    Base (int);
};

struct Derived : public Base {
    Derived (int);
};

Derived :: Derived (int i)
: Base (i)
{
}

Answer 4

class Parent
{
    // Parent Constructor
    Parent(int x)
    {
        // Constructor Code
    }
};

class Child : public Parent
{
    // Child Constructor  
    Child(int x, int y, int z) : Parent(x)
    {
        // Constructor Code
    }
};