Is it possible to create lambda methods of a particular class?

Question

For instance I have

class A {
public:
    int x, y;
    int(*func)();
};

and I would like to make that func be something like

int main()
{
    A a;
    a.func = [this](){return x + y;};
}

or something like that. That would mean that I can create method "func" during runtime and decide what it is. Is it possible in C++?

Jake · Accepted Answer · 2013-08-13 17:52:44Z

1

It is sorta possible but only using captures which would mean you would need to use std::function<> instead. It wont have nice 'this' behavior like you wanted I think

struct A {
  int x, y;
  std::function<int()> func;
};

and then code like this

int main() {
    A self;
    test.func = [&self](){ return self.x + self.y; };
}

I never say never in C++ (even with goto) but I'm rather unsure that this would actually be a good way to do things. Yes, you CAN do this but are you sure there isn't a better way? Food for thought.

answered Aug 13, 2013 at 17:52

Jake

7571 gold badge5 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

anthonyvd Over a year ago

Or make the lambda receive a parameter of type A, although that's not particularly more elegant.

Artem Over a year ago

Jake, so the only way is to pass it as an argument or to make visible? It's so sad, I thought that it's possible to do like in JS.

Jake Over a year ago

That would require you to call it like test.func(test) which reminds me too much of me trying to mimic OOP in C lol.

Artem Over a year ago

And is it going to work fine if I have an array: A a[10]; for (int i = 0; i < 10; i++) a[i].func = [a[i]](){ a[i].x=5;};

Jake Over a year ago

@Artem: Well I'm certain that 'this' is not in scope outside of a member function definition and that it would be an error to use it elsewhere. I'm also certain that if you want to avoid 'test.func(test)' you either have to capture the variable or partially apply it using std::bind. either way you don't get 'this'

|

Collectives™ on Stack Overflow

Is it possible to create lambda methods of a particular class?

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related