Event listener primitives

This crate provides a low-level primitive for building Node.js-like event listeners.

The 3 primitives are Bag that is a container for Fn() event handlers, BagOnce the same for FnOnce() event handlers and HandlerId that will remove event handler from the bag on drop.

Trivial example: ```rust use eventlistenerprimitives::{Bag, HandlerId};

fn main() { let bag = Bag::default();

let handler_id = bag.add(move || {
    println!("Hello")
});

bag.call_simple();

} ```

Close to real-world usage example:

```rust use eventlistenerprimitives::{Bag, BagOnce, HandlerId};

[derive(Default)]

struct Handlers { action: Bag>, closed: BagOnce>, }

pub struct Container { handlers: Handlers, }

impl Drop for Container { fn drop(&mut self) { self.handlers.closed.call_simple(); } }

impl Container { pub fn new() -> Self { let handlers = Handlers::default();

    Self { handlers }
}

pub fn do_action(&self) {
    // Do things...

    self.handlers.action.call_simple();
}

pub fn do_other_action(&self) {
    // Do things...

    self.handlers.action.call(|callback| {
        callback();
    });
}

pub fn on_action<F: Fn() + Send + Sync + 'static>(&self, callback: F) -> HandlerId {
    self.handlers.action.add(Box::new(callback))
}

pub fn on_closed<F: FnOnce() + Send + Sync + 'static>(&self, callback: F) -> HandlerId {
    self.handlers.closed.add(Box::new(callback))
}

}

fn main() { let container = Container::new(); let onactionhandlerid = container.onaction(|| { println!("On action"); }); container .onclosed(|| { println!("On container closed"); }) .detach(); // This will trigger "action" callback just fine since its handler ID is not dropped yet container.doaction(); drop(onactionhandlerid); // This will not trigger "action" callback since its handler ID was already dropped container.doother_action(); // This will trigger "closed" callback though since we've detached handler ID drop(container);

println!("Done");

} ```

The output will be: text On action On closed Done

Contribution

Feel free to create issues and send pull requests, they are highly appreciated!

License

Zero-Clause BSD

https://opensource.org/licenses/0BSD

https://tldrlegal.com/license/bsd-0-clause-license