signal_type add a rvalue operator

[qicosmos]

hi, the signal_type's opertator is just surpport lvalue, it need a rvalue version, like this.

void operator()(A&&... args) const {
    for (auto const& slot : copy_slots()) {
        if (slot) {
                  slot(std::forward<A>(args)...);
            }
    }
}

[fr00b0]

Hello,
I'm currently looking into this, but I'm not convinced that it's a good idea to implement. Doing a std::forward in a loop like that will open up some cans of worms.

If I were to add the implementation to the library, the code below will fail catastrophically since the first slot will consume the argument:

auto lambda =
    [&]( std::unique_ptr<int> value ) {
        std::cout << *value << std::endl;
    };

nod::signal<void(std::unique_ptr<int>&&)> signal;
signal.connect( lambda );
signal.connect( lambda );
signal( std::make_unique<int>( 5 ) );

When I get some more time to sit down, I'll look into this some more.

If you don't mind me asking, what are the situation where you need the rvalue version?

[qicosmos]

hello,
it is meaningless to use rvalue in loop, i just make a unit test, and the code can't be compiled.
this is the code:

    nod::signal<void(string&&)> signal;
    signal.connect([](string&& i){});
    signal(string(""));

so i have to add a rvalue version.

[fr00b0]

Yes I understand that your code will not compile. I'm curious about the situation where you need a signal with a rvalue argument. Will you move arguments into your signals? What happens if that signal has multiple slots connected when it is triggered?

[qicosmos]

I konw your meaning. a rvalue argument in this situation is meaningless. I think you could give some advice to user, maybe somebody makes a mistake.

[fr00b0]

I'm closing this issue as it's not implementable, but the issue lives on in issue #12