actix/fut/try_future/
and_then.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
use std::{
    pin::Pin,
    task::{Context, Poll},
};

use futures_util::ready;
use pin_project_lite::pin_project;

use crate::{
    actor::Actor,
    fut::{future::ActorFuture, try_future::ActorTryFuture},
};

pin_project! {
    /// Future for the `and_then` combinator, chaining computations
    /// on the end of another actor future regardless of its outcome.
    ///
    /// This is created by the `ActorTryFuture::and_then` method.
    #[project = AndThenProj]
    #[derive(Debug)]
    #[must_use = "futures do nothing unless polled"]
    pub enum AndThen<A, B, F> {
        First {
            #[pin]
            fut1: A,
            data: Option<F>,
        },
        Second {
            #[pin]
            fut2: B
        },
        Empty,
    }
}

pub(super) fn new<A, B, F, Act>(future: A, f: F) -> AndThen<A, B, F>
where
    A: ActorTryFuture<Act>,
    B: ActorTryFuture<Act>,
    Act: Actor,
{
    AndThen::First {
        fut1: future,
        data: Some(f),
    }
}

impl<A, B, F, Act> ActorFuture<Act> for AndThen<A, B, F>
where
    A: ActorTryFuture<Act>,
    B: ActorTryFuture<Act, Error = A::Error>,
    F: FnOnce(A::Ok, &mut Act, &mut Act::Context) -> B,
    Act: Actor,
{
    type Output = Result<B::Ok, A::Error>;

    fn poll(
        mut self: Pin<&mut Self>,
        act: &mut Act,
        ctx: &mut Act::Context,
        task: &mut Context<'_>,
    ) -> Poll<Self::Output> {
        match self.as_mut().project() {
            AndThenProj::First { fut1, data } => {
                let ok = ready!(fut1.try_poll(act, ctx, task))?;
                let data = data.take().unwrap();
                let fut2 = data(ok, act, ctx);
                self.set(AndThen::Second { fut2 });
                self.poll(act, ctx, task)
            }
            AndThenProj::Second { fut2 } => {
                let res = ready!(fut2.try_poll(act, ctx, task));
                self.set(AndThen::Empty);
                Poll::Ready(res)
            }
            AndThenProj::Empty => panic!("ActorFuture polled after finish"),
        }
    }
}