Possible Duplicate:
Is there a difference in C++ between copy initialization and direct initialization?
Class A
{
public:
//some member function call
private:
int x;
char a;
};
int main()
{
A a;
A b;
}
Hi can You tell me the Difference's in Between these when I call or initialize the objects of above class as
A a(b);
A a=b;
a=b;
The first 2 lines calls the copy constructor because the objects are being constructed. The last line will call the equals operator to perform the assignment.
A a(b);
A a = b;
These use the implicitly generated copy constructor.
a = b;
This one uses the assignment operator, and it is not an initialization, since it does not create an A object: it just gives a new value to an existing one.
The copy constructor would have a signature such as
A(const A&);
and the assignment operator
A& operator=(const A&);
Since your class doesn't provide these, the compiler synthesizes them and just copies the data members.
Since your class doesnt have any explicit copy constructor all of the above statements results in shallow copy.
If you have declared a copy constructor and overloaded the = operator then
A a(b) and A a= b will result in calling the copy constructor and
a= b will result in calling the = overloaded operator
Read this for more understanding
