C++ - how to reinitialize object repeatedly?

Question

I'm trying to implement this logic in C++:

Object obj(args);
while (obj.isOK()) {
    obj = obj.next();
}

But I can't use this exact code because Object inherits boost::noncopyable so it has no assignment operator. I can add methods and constructors to Object, (but not make it copyable), however I would prefer not to. Other questions have manual destruction and placement new as a solution, which I could do if I create a new constructor for Object, but again, preferably I wouldn't need the new constructor, and that seems like a pretty nasty solution anyway. What alternatives do I have?

If Object is trivially copyable and destructable, you could probably memcpy it around. — Weak to Enuma Elish, Nov 08 '15 at 08:06
@JamesRoot We should assume the class has been made non-copyable for a reason. — juanchopanza, Nov 08 '15 at 08:56
@drew If it's truly being constructed like `Object obj(args);` wouldn't that mean a user-defined constructor and therefore not a POD? — Weak to Enuma Elish, Nov 08 '15 at 08:57
Yep, I've removed that comment. I thought POD encompassed more types than it actually does. My bad. — Drew, Nov 08 '15 at 09:05

score 3 · Accepted Answer · answered Nov 08 '15 at 08:06

3

Make Object::next mutate the Object in place. Since Object is not copyable, this seems like the only sensible thing for Object::next to do anyway.

answered Nov 08 '15 at 08:06

Brian Bi

111,498
10
176
312

score -1 · Answer 2 · answered Nov 08 '15 at 10:23

What does Object::next return? If it returns a fresh Object you could add a move-assignment operator to Object:

Object& operator=(Object&& obj)
{
    //move its iternal state to this and then
    return *this;
}

So no data duplication takes place and nothing is actually copied.

C++ - how to reinitialize object repeatedly?

2 Answers2