Copy Constructor Call When Function Returns a Reference to Class Object – Computer Sir Ki Class


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Copy Constructor Call When Function Returns a Reference to Class Object

Understanding copy constructor call when a function is returning reference to a class object.

Learning Objectives

  • Viewing how copy constructor is called when a function returns a reference to an object.

Source Code

TC++ #7473


Source Code

Run Output


Code Understanding

int x,y;  //Global variables declared so that this demo allows them to use from different functions.
class C { //Class C declared
C(){ x=10;}  //Default Constructor sets x as 10.
C(C& D) { x=20;} //Copy Constructor sets x as 20.

C E;               //An object E of class type C has been declared. This has been declared globally so that the returned reference can be used by other functions or objects.

C& func() {//This functions is returning a reference to Class type C
return E;      //A reference to object E is returned.

int main(){
C c1;    //c1 is an object based on C, so just default constructor would be called.
cout<<x<<endl; //This prints 10 as default constructor has set x as 10.
C c2=func();    //Here another object c2 is being made based on object reference returned by function func()
cout<<x<<endl; //This would print 20 as copy constructor has now been called.
return 0;}


  • Copying copy constructor can be called in many other situations like
    – Creating copy of an object.
    – When Object is called by value to a function.
    – When Object is returned from a function.
    – When temporary objects are created.

Common Errors

  • If function doesn’t return object by reference like this C func() then compilation error would occur.
  • If the the object  C E; is declared inside the function the returned reference may not be available to other functions and error/warning may be returned by the compiler.

Suggested Filename(s): objreturnedasreference.cpp,obretref.cpp


CSKC| Created: 26-Apr-2019 | Updated: 26-Apr-2019|

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