10

20

Code Understanding

int x,y;  //Global variables declared so that this demo allows them to use from different functions.
class C { //Class C declared
public:
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;}

Notes

• 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