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C++ Programming for Experienced Engineers

Sequence for Calling Constructors

Explore how constructor calls are sequenced when creating derived class objects in C++ inheritance. Understand the importance of calling base class constructors explicitly and how this affects object initialization, especially in multi-level inheritance scenarios.

We'll cover the following...

Problem

Write a program that displays the sequence for calling constructors during inheritance.

Coding solution

Here is a solution to the problem above.

C++
// Constructor inheritance
#include <iostream>
class Sample
{
	protected :
		int count ;
		
	public :
		
		Sample( )
		{
			count = 0 ;
			std :: cout << "Reached 0-arg Ctor of Sample" << std :: endl ;
		}
	
		Sample ( int k )
		{
			count = k ;
			std :: cout << "Reached 1-arg Ctor of Sample" << std :: endl ;
		}
} ;
class NewSample : public Sample
{
	private :
		int newcount ;
		
	public :
		NewSample( )
		{
			newcount = count * 20 ;
			std :: cout << "Reached 0-arg Ctor of NewSample" << std :: endl ;
		}
	
		NewSample ( int k ) : Sample ( k )
		{
			newcount = count * 20 ;
			std :: cout << "Reached 1-arg Ctor of NewSample" << std :: endl ;
		}
} ;
int main( )
{
	std :: cout << "Ctor calling order for i :" << std :: endl ;
	Sample i ;
	
	std :: cout << "Ctor calling order for j :" << std :: endl ;
	NewSample j ;
	
	std :: cout << "Ctor calling order for k :" << std :: endl ;
	NewSample k ( 30 ) ;
}
...