Event handler lifetime shouldn't be static

[doraeric]

rust-socketio/socketio/src/client/builder.rs

Lines 169 to 172 in 095db3a

	pub fn on<T: Into<Event>, F>(mut self, event: T, callback: F) -> Self
	where
	F: FnMut(Payload, RawClient) + 'static + Send,
	{

Currently, when building client with event handler, the lifetime of the event handler is required to be static, but I think it should be as long as the client instance.
I want to pass some objects, queue for example, to handlers without transferring ownership. It seems impossible at the moment.

This is the code that I want to use

{
    let (tx, rx) = channel::<String>();
    let callback = |payload: Payload, socket: RawClient| {
        tx.send("...");
    };
    let callback2 = |payload: Payload, socket: RawClient| {
        tx.send("...");
    };
    let socket = ClientBuilder::new(url)
        .on("evt1", callback)
        .on("evt2", callback2)
        .connect()
        .expect("Connection failed");
}

[doraeric]

I just found that crossbeam_channel works for me since the sender can be cloned. But I still think the handler should have shorter lifetime.

[1c3t3a]

Fair point! Didn't think about this in the implementation. I am very happy to accept a PR for this!

[vishalcjha]

@doraeric In your example, you are missing move for tx. Once you do that it should work.

{
    let (tx, rx) = channel::<String>();
    let tx_clone = tx.clone();
    let callback = move |payload: Payload, socket: RawClient| {
        tx_clone.send("...");
    };
    let callback2 = move |payload: Payload, socket: RawClient| {
        tx.send("...");
    };
    let socket = ClientBuilder::new(url)
        .on("evt1", callback)
        .on("evt2", callback2)
        .connect()
        .expect("Connection failed");
}

[HuakunShen]

@vishalcjha How to transform your example code to use async? I had a lot of trouble with this.

For example

#[tokio::main]
async fn main() {
    let (tx, rx) = channel::<String>();
    let tx_clone = tx.clone();
    let callback = |payload: Payload, socket: Client| {
        async move {
            tx_clone.send("...".to_string());
        }.boxed()
    };
    let callback2 = |payload: Payload, socket: Client| {
        async move {
            tx.send("...".to_string());
        }.boxed()
    };
    let socket = ClientBuilder::new("")
        .on("evt1", callback)
        .on("evt2", callback2)
        .connect()
        .await
        .expect("Connection failed");
}

Always gives error:

expected a closure that implements the `FnMut` trait, but this closure only implements `FnOnce`
this closure implements `FnOnce`, not `FnMut`