callbag 0.14.0

Rust implementation of the callbag spec for reactive/iterable programming
Documentation 
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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120

use arc_swap::ArcSwapOption;
use std::sync::Arc;

use crate::{Message, Source};

/// Callbag sink that consumes both pullable and listenable sources.
///
/// When called on a pullable source, it will iterate through its data. When called on a listenable
/// source, it will observe its data.
///
/// See <https://github.com/staltz/callbag-for-each/blob/a7550690afca2a27324ea5634a32a313f826d61a/readme.js#L40-L47>
///
/// # Examples
///
/// Consume a pullable source:
///
/// ```
/// use crossbeam_queue::SegQueue;
/// use std::sync::Arc;
///
/// use callbag::{for_each, from_iter};
///
/// let actual = Arc::new(SegQueue::new());
///
/// let source = from_iter([10, 20, 30, 40]);
///
/// for_each({
///     let actual = Arc::clone(&actual);
///     move |x| {
///         println!("{}", x);
///         actual.push(x);
///     }
/// })(source);
///
/// assert_eq!(
///     &{
///         let mut v = vec![];
///         for _i in 0..actual.len() {
///             v.push(actual.pop().unwrap());
///         }
///         v
///     }[..],
///     [10, 20, 30, 40]
/// );
/// ```
///
/// Consume a listenable source:
///
/// ```
/// use async_executors::TimerExt;
/// use async_nursery::Nursery;
/// use crossbeam_queue::SegQueue;
/// use std::{sync::Arc, time::Duration};
///
/// use callbag::{for_each, interval};
///
/// let (nursery, nursery_out) = Nursery::new(async_executors::AsyncStd);
///
/// let actual = Arc::new(SegQueue::new());
///
/// let source = interval(Duration::from_millis(1_000), nursery.clone());
///
/// for_each({
///     let actual = Arc::clone(&actual);
///     move |x| {
///         println!("{}", x);
///         actual.push(x);
///     }
/// })(source);
///
/// let nursery_out = nursery.timeout(Duration::from_millis(4_500), nursery_out);
/// drop(nursery);
/// async_std::task::block_on(nursery_out);
///
/// assert_eq!(
///     &{
///         let mut v = vec![];
///         for _i in 0..actual.len() {
///             v.push(actual.pop().unwrap());
///         }
///         v
///     }[..],
///     [0, 1, 2, 3]
/// );
/// ```
pub fn for_each<T: 'static, F: 'static, S>(f: F) -> Box<dyn Fn(S)>
where
    F: Fn(T) + Send + Sync + Clone,
    S: Into<Arc<Source<T>>>,
{
    Box::new(move |source| {
        let source: Arc<Source<T>> = source.into();
        let talkback = ArcSwapOption::from(None);
        source(Message::Handshake(Arc::new(
            {
                let f = f.clone();
                move |message| match message {
                    Message::Handshake(source) => {
                        talkback.store(Some(source));
                        let talkback = talkback.load();
                        let talkback = talkback.as_ref().expect("source talkback not set");
                        talkback(Message::Pull);
                    },
                    Message::Data(data) => {
                        f(data);
                        let talkback = talkback.load();
                        let talkback = talkback.as_ref().expect("source talkback not set");
                        talkback(Message::Pull);
                    },
                    Message::Pull => {
                        panic!("source must not pull");
                    },
                    Message::Error(_) => {},
                    Message::Terminate => {},
                }
            }
            .into(),
        )));
    })
}