Overload a class constructor that takes an rvalue reference

Question

I would like to do something like the following:

class Foo
{
    Foo(int &&a, int b, std::string s="");
    // does not compile because a is not an rvalue:
    // Foo(int &&a, std::string s) : Foo(a, 0, s) {}
    Foo(int &&a, std::string s) : Foo(std::move(a), 0, s) {} // move a
}

Is this a valid way to overload a constructor in general?
And specifically one that takes an rvalue reference as a parameter?

Edited based on comments

To clarify, I'm new to move semantics (and an amateur programmer) and I'm simply not sure if this is a good way to handle this situation.

I added the first question based on a comment (now deleted) that suggested this is not the correct way to overload constructors.

Why don't you want to use `std::move`? What do you mean by "better"? — Rakete1111, Nov 17 '18 at 17:59
If it did compile, the default argument would make which constructor to call ambiguous. — , Nov 17 '18 at 18:01
As you already recognized `std::move` is the right way to do it. — Werner Henze, Nov 17 '18 at 18:01
Thanks for your comments. I've edited the question accordingly. @Ripi2 I'll look into what is. — bur, Nov 17 '18 at 18:07

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

Is this a valid way to overload a constructor in general?

And specifically one that takes an rvalue reference as a parameter?

It is valid to overload constructors in general, even ones that have rvalue reference arguments.

In particular, your example is ill-formed. As you point out in the comments, the example fails to compile. To fix it, you must pass an rvalue to the constructor that you delegate to. The correct way to convert a rvalue reference variable into an rvalue is to use std::move. So, what you must do is what you already know:

The only option I can see is to std::move(a).

edited Jun 20 '20 at 09:12

Community

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answered Nov 17 '18 at 18:12

eerorika

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To future readers: I edited the question before I saw this answer. Thanks, this answers my second question, and I can infer that the answer to my first question is yes. – bur Nov 17 '18 at 18:19

Overload a class constructor that takes an rvalue reference

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