delegating constructor c++11

delegating constructor

C++11 extends the scope of constructor. Now constructor can call another constructor of same class. such constructors are called as “delegating constructors”, it delegates the request to another constructor.

Use Case:

We have common functionalities across two or more constructors.

Solution:  We can add new function named as init() and we can keep these common functionalities in init() function and can call this from all constructors.

Solution After C++11: We can keep these common functionalities in one constructor and other constructors can call that constructor. Calling constructors are called as delegating constructor because they are delegating the request.

Objective/Purpose:

We can keep common functionalities in one constructor and reduce the writing affords and remove the duplicate code.

Note: Below example is meant only for explaining the above topic.

source code with example:

/*
Program: Delegating Constructor 
Author: Alpha Master
Date: 9 March 2021
*/

//Header File
#include<iostream>

class test {};

class sample
{
int mIa;

public:
   sample()    //equivalent to init() function
   {
       test t;
       std::cout<<"test object creation"<<std::endl;
   }
   sample(int tmp): mIa(tmp)
   {
       sample();
   }
   sample(double tmp)
   {
        mIa = tmp;
        sample();
   }

};


int main()
{
    std::cout<<"Delegating Constructor"<<std::endl;
    sample(5);
    sample(5.5);
    return 0;
}

Output:

Delegating Constructor
test object creation
test object creation