Copy constructor and Assignment operator are similar as they are both used to initialize one object using another object. But, there are some basic differences between them:
| Copy constructor | Assignment operator |
|---|
| It is called when a new object is created from an existing object, as a copy of the existing object | This operator is called when an already initialized object is assigned a new value from another existing object. |
| It creates a separate memory block for the new object. | It does not automatically create a separate memory block or new memory space. However, if the class involves dynamic memory management, the assignment operator must first release the existing memory on the left-hand side and then allocate new memory as needed to copy the data from the right-hand side. |
| It is an overloaded constructor. | It is a bitwise operator. |
| C++ compiler implicitly provides a copy constructor, if no copy constructor is defined in the class. | A bitwise copy gets created, if the Assignment operator is not overloaded. |
Syntax: className(const className &obj) { // body } | Syntax: className obj1, obj2; obj2 = obj1; |
Consider the following C++ program.
CPP// CPP Program to demonstrate the use of copy constructor// and assignment operator#include<iostream>#include<stdio.h>usingnamespacestd;classTest{public:Test(){}Test(constTest&t){cout<<"Copy constructor called "<<endl;}Test&operator=(constTest&t){cout<<"Assignment operator called "<<endl;return*this;}};// Driver codeintmain(){Testt1,t2;t2=t1;Testt3=t1;getchar();return0;}OutputAssignment operator called Copy constructor called
Explanation:Here,t2 = t1; calls theassignment operator, same ast2.operator=(t1); and Test t3 = t1; calls thecopy constructor, same asTest t3(t1);
Must Read:When is a Copy Constructor Called in C++?