CODEWITHSUNDEEP
c++constructoroperator-overloading
IzonFreak
IzonFreak

Reputation: 409

why is this happening ? operator= and copy constructor

I have the following classes:

class CRectangle
{
    CRectangle(string color);
    CRectangle(CRectangle &origin);
    /* Some more code */
};

and this other:

class CPlane
{
    /* Some more code */
    CRectangle boundingBox();
};

Why is it that I can do this? :

CRectangle rectangle1;
CRectangle rectangle2=rectangle1;
CRectangle rectangle3(rectangle1); //Copy constructor.

But I can't do this:

CPlane plane;
CRectangle rectangle4=plane.boundingBox();
CRectangle rectangle5(plane.boundingBox()); //Copy constructor.

If I need to me the last one work how can I do it? I suppose that maybe it has something to do with operator = but I don't know exactly.

Edit: to fix copy constructor. error still there.

Upvotes: 3

Views: 130

Answers (2)

Columbo
Columbo

Reputation: 60979

You cannot bind rvalues to a non-const lvalue reference.

CRectangle rectangle3(rectangle1);

Here rectangle1 is a non-const lvalue, so that's fine.

CRectangle rectangle5(plane.boundingBox());

plane.boundingBox() is a pure rvalue (prvalue), so CRectangle& cannot be bound to it.

Instead declare your copy constructor to take a const reference:

CRectangle(CRectangle const&);

Or additionally declare a move constructor (if desired).

Upvotes: 3

ravi
ravi

Reputation: 10733

First syntax of your copy constructor request compiler for infinite recursion.

It should be:-

CRectangle(const CRectangle& origin);

Second, both call should work properly as both are calls to copy constrcutor.

CRectangle rectangle4=plane.boundingBox();
CRectangle rectangle5(plane.boundingBox());

Upvotes: 5

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