Use of COPY CONSTRUCTORS

[dakuneko]

Can anyone tell me where I can use the copy constructor? ~~~
"In C++, only friends can touch your private parts." - Emmanuel Ackouoy

 

[pipk]

I may be mistaken but I believe that the copy constructor is automatically called whenever you make a call-by-value function call, passing your user defined class as a parameter.

It is definately required if you have a user defined class that dynamically allocates memory (from the heap).

 

[abp]

Copy constructors are not automatically called when you pass class objects to functions. Instead you need to have a copy constructor in your class. Copy constructors are useful ....

1.If you have an object of a particular class.
2. You need to make a copy of the object(members
have the same value) in a different memory space.

For egs. Assume you have class A.
class A
{
A();
~A();
...
};

You allocate an object of A

A a1;

You need to make a "copy" of a1 but the members shouldnt
reference members of a1 in memory. If you use normal(bitwise) copy like...

A a2 = a1;

a2 will refer to the same piece of allocated memory that a1 is using. So if you delete a2 ,the memory of a1 will also be deleted. Instead if u use a copy constructor to initialize a2 this wont happen.

A a2(a1);

THe usual declaration for a copy constructor is

A::A(const A &a) {

/* create memory and initialize object here */

}


Hope this helps.

Best regards,
abp