rx_rust/operators/combining/
combine_latest.rs

1use crate::safe_lock_option_observer;
2use crate::utils::types::{Mutable, MutableHelper, NecessarySendSync, Shared};
3use crate::{
4    disposable::subscription::Subscription,
5    observable::Observable,
6    observer::{Observer, Termination},
7    utils::unsub_after_termination::subscribe_unsub_after_termination,
8};
9use educe::Educe;
10
11/// Combines multiple Observables to create an Observable whose values are calculated from the latest values of each of its input Observables.
12/// See <https://reactivex.io/documentation/operators/combinelatest.html>
13///
14/// # Examples
15/// ```rust
16/// use rx_rust::{
17///     observable::observable_ext::ObservableExt,
18///     observer::{Observer, Termination},
19///     operators::combining::combine_latest::CombineLatest,
20///     subject::behavior_subject::BehaviorSubject,
21/// };
22/// use std::convert::Infallible;
23///
24/// let mut values = Vec::new();
25/// let mut terminations = Vec::new();
26///
27/// let mut subject_1 = BehaviorSubject::<'_, i32, Infallible>::new(0);
28/// let mut subject_2 = BehaviorSubject::<'_, i32, Infallible>::new(10);
29///
30/// let subscription =
31///     CombineLatest::new(subject_1.clone(), subject_2.clone()).subscribe_with_callback(
32///         |value| values.push(value),
33///         |termination| terminations.push(termination),
34///     );
35///
36/// subject_1.on_next(1);
37/// subject_2.on_next(11);
38/// subject_1.on_termination(Termination::Completed);
39/// subject_2.on_termination(Termination::Completed);
40/// drop(subscription);
41///
42/// assert_eq!(values, vec![(0, 10), (1, 10), (1, 11)]);
43/// assert_eq!(terminations, vec![Termination::Completed]);
44/// ```
45#[derive(Educe)]
46#[educe(Debug, Clone)]
47pub struct CombineLatest<OE1, OE2> {
48    source_1: OE1,
49    source_2: OE2,
50}
51
52impl<OE1, OE2> CombineLatest<OE1, OE2> {
53    pub fn new<'or, 'sub, T1, T2, E>(source_1: OE1, source_2: OE2) -> Self
54    where
55        OE1: Observable<'or, 'sub, T1, E>,
56        OE2: Observable<'or, 'sub, T2, E>,
57    {
58        Self { source_1, source_2 }
59    }
60}
61
62impl<'or, 'sub, T1, T2, E, OE1, OE2> Observable<'or, 'sub, (T1, T2), E> for CombineLatest<OE1, OE2>
63where
64    T1: Clone + NecessarySendSync + 'or,
65    T2: Clone + NecessarySendSync + 'or,
66    OE1: Observable<'or, 'sub, T1, E>,
67    OE2: Observable<'or, 'sub, T2, E>,
68    'sub: 'or,
69{
70    fn subscribe(
71        self,
72        observer: impl Observer<(T1, T2), E> + NecessarySendSync + 'or,
73    ) -> Subscription<'sub> {
74        subscribe_unsub_after_termination(observer, |observer| {
75            let observer = Shared::new(Mutable::new(Some(observer)));
76            let context = Shared::new(Mutable::new(CombineLatestContext {
77                latest_1: None,
78                latest_2: None,
79                should_completed: false,
80            }));
81            let observer_1 = CombineLatestObserver1 {
82                context: context.clone(),
83                observer: observer.clone(),
84            };
85            let observer_2 = CombineLatestObserver2 { context, observer };
86            let subscription_1 = self.source_1.subscribe(observer_1);
87            let subscription_2 = self.source_2.subscribe(observer_2);
88            subscription_1 + subscription_2
89        })
90    }
91}
92
93struct CombineLatestContext<T1, T2> {
94    latest_1: Option<T1>,
95    latest_2: Option<T2>,
96    should_completed: bool,
97}
98
99struct CombineLatestObserver1<T1, T2, OR> {
100    context: Shared<Mutable<CombineLatestContext<T1, T2>>>,
101    observer: Shared<Mutable<Option<OR>>>,
102}
103
104impl<T1, T2, E, OR> Observer<T1, E> for CombineLatestObserver1<T1, T2, OR>
105where
106    T1: Clone,
107    T2: Clone,
108    OR: Observer<(T1, T2), E>,
109{
110    fn on_next(&mut self, latest_1: T1) {
111        self.context.lock_mut(|mut lock| {
112            lock.latest_1 = Some(latest_1.clone());
113            if let Some(latest_2) = lock.latest_2.clone() {
114                drop(lock);
115                safe_lock_option_observer!(on_next: self.observer, (latest_1, latest_2));
116            }
117        });
118    }
119
120    fn on_termination(self, termination: Termination<E>) {
121        match termination {
122            Termination::Completed => {
123                self.context.lock_mut(|mut lock| {
124                    if lock.should_completed || lock.latest_1.is_none() {
125                        drop(lock);
126                        safe_lock_option_observer!(on_termination: self.observer, termination);
127                    } else {
128                        lock.should_completed = true;
129                    }
130                });
131            }
132            Termination::Error(_) => {
133                safe_lock_option_observer!(on_termination: self.observer, termination);
134            }
135        }
136    }
137}
138
139struct CombineLatestObserver2<T1, T2, OR> {
140    context: Shared<Mutable<CombineLatestContext<T1, T2>>>,
141    observer: Shared<Mutable<Option<OR>>>,
142}
143
144impl<T1, T2, E, OR> Observer<T2, E> for CombineLatestObserver2<T1, T2, OR>
145where
146    T1: Clone,
147    T2: Clone,
148    OR: Observer<(T1, T2), E>,
149{
150    fn on_next(&mut self, latest_2: T2) {
151        self.context.lock_mut(|mut lock| {
152            lock.latest_2 = Some(latest_2.clone());
153            if let Some(latest_1) = lock.latest_1.clone() {
154                drop(lock);
155                safe_lock_option_observer!(on_next: self.observer, (latest_1, latest_2));
156            }
157        });
158    }
159
160    fn on_termination(self, termination: Termination<E>) {
161        match termination {
162            Termination::Completed => {
163                self.context.lock_mut(|mut lock| {
164                    if lock.should_completed || lock.latest_2.is_none() {
165                        drop(lock);
166                        safe_lock_option_observer!(on_termination: self.observer, termination);
167                    } else {
168                        lock.should_completed = true;
169                    }
170                });
171            }
172            Termination::Error(_) => {
173                safe_lock_option_observer!(on_termination: self.observer, termination);
174            }
175        }
176    }
177}
rx_rust/operators/combining/combine_latest.rs

rx_rust/operators/combining/
combine_latest.rs
