Hello,

I'm trying to find, in rust, in the most idiomatic way, to represent a resource (in a struct) that is to be initialized but in the future. Not in the new function.

Would it be better to use Option or Box ? Or is there a better option ?

In my specific case I have a struct meant to implement the Future trait. The main function of the future that I call (I didn't write the function, the code isn't mine, I use a third C library) has a callback as an argument that is called when the result is ready.

It looks something like this:

struct MyFutureStruct {
     // ...some other ressources....
     result_created: bool,
     waker: Option<Waker> // is this good ? or should I use Box or something else ?
}

impl Future for MyFutureStruct {
   type Output = ...;

    fn poll(self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Self::Output> {
       match self.result_created {
           false => {
              // something like this - more like a pseudo code here
              // this callback is called when the result is created and ready to be used 
              self.waker  = Some(ctx.waker().clone());
              let callback = result_created_callback
              // call the main third library function here
              create_result(callback)
           }
           true => {
              // here the callback was called
           }
       }
    }

    fn result_callback_created(user_data) {
       // here user_data is Self
       self.waker.unwrap().wake_by_ref()
       self.result_created = true
    }
}

As you can see, I'm not sure whether Option is the best way to contain the Waker.

Hoping I was clear enough.

Thank you very much in advance for any help.

3 posts - 2 participants

Read full topic