Prev: Assignment operator definition required in case of reference data member why?
Next: why should you use c++ in such project ?
From: Nick Hounsome on 15 May 2010 06:55
On 14 May, 16:51, "Daya S. Prasad" <mail....(a)gmail.com> wrote:
> Consider a code:
>
> class B { };
>
> class TestClass {
> B &obj;
> public:
> TestClass(B &refObj) : obj(refObj) {
> cout << "Called ... TestClass(B &refObj)\n";
> }
> TestClass & operator=(TestClass const &) {
> cout << "Called ... TestClass & operator=(TestClass const &)\n";
> return *this;
> }
> ~TestClass() {
> cout << "Called ... ~TestClass()\n";
> }
>
> };
>
> B b_obj;
> TestClass obj1(b_obj), obj2(b_obj);
> obj1 = obj2;
>
> Above posted code works perfectly until and unless we've defined
> assignment operator. As soon as we remove overloaded assignment
> operator it throws compilation error.
>
> error: non-static reference member 'B& TestClass::obj', can't use
> default assignment operator
> note: synthesized method 'TestClass& TestClass::operator=(const
> TestClass&)' first required here
>
> Can anybody please tell me exactly what's the reason for compilation
> error. As per my understanding this error comes due to B &
> TestClass::obj but reference is also an object with different name and
> B can use its default assignment operator for assignment. Overall
> TestClass is perfectly assignable class without overloaded assignment
> operator. Then why compilation error? and why it removes when simply
> define overloaded assignment operator?

It might help to realise that, the compiler effectively implements obj
as

B* const obj;

So the default assignment would be trying to change an const object.


--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]

 | 
Pages: 1
Prev: Assignment operator definition required in case of reference data member why?
Next: why should you use c++ in such project ?