rx_rust/operators/combining/
switch.rs

1use crate::disposable::Disposable;
2use crate::disposable::subscription::Subscription;
3use crate::utils::types::{Mutable, MutableHelper, NecessarySendSync, Shared};
4use crate::{
5    observable::Observable,
6    observer::{Observer, Termination},
7    operators::creating::from_iter::FromIter,
8    utils::{types::MarkerType, unsub_after_termination::subscribe_unsub_after_termination},
9};
10use crate::{safe_lock_option, safe_lock_option_disposable, safe_lock_option_observer};
11use educe::Educe;
12use std::marker::PhantomData;
13
14/// Converts an Observable that emits Observables into a single Observable that emits the items emitted by the most recently emitted of those Observables.
15/// See <https://reactivex.io/documentation/operators/switch.html>
16///
17/// # Examples
18/// ```rust
19/// use rx_rust::{
20///     observable::observable_ext::ObservableExt,
21///     observer::Termination,
22///     operators::{
23///         combining::switch::Switch,
24///         creating::from_iter::FromIter,
25///     },
26/// };
27///
28/// let mut values = Vec::new();
29/// let mut terminations = Vec::new();
30///
31/// let inner_1 = FromIter::new(vec![1, 2]);
32/// let inner_2 = FromIter::new(vec![3, 4]);
33/// let observable = Switch::new_from_iter([inner_1, inner_2]);
34/// observable.subscribe_with_callback(
35///     |value| values.push(value),
36///     |termination| terminations.push(termination),
37/// );
38///
39/// assert_eq!(values, vec![1, 2, 3, 4]);
40/// assert_eq!(terminations, vec![Termination::Completed]);
41/// ```
42#[derive(Educe)]
43#[educe(Debug, Clone)]
44pub struct Switch<OE, OE1> {
45    source: OE,
46    _marker: MarkerType<OE1>,
47}
48
49impl<OE, OE1> Switch<OE, OE1> {
50    pub fn new<'or, 'sub, T, E>(source: OE) -> Self
51    where
52        OE: Observable<'or, 'sub, OE1, E>,
53        OE1: Observable<'or, 'sub, T, E>,
54    {
55        Self {
56            source,
57            _marker: PhantomData,
58        }
59    }
60}
61
62impl<OE1, I> Switch<FromIter<I>, OE1> {
63    pub fn new_from_iter<'or, 'sub, T, E>(into_iterator: I) -> Self
64    where
65        I: IntoIterator<Item = OE1>,
66        OE1: Observable<'or, 'sub, T, E>,
67    {
68        Self {
69            source: FromIter::new(into_iterator),
70            _marker: PhantomData,
71        }
72    }
73}
74
75impl<'or, 'sub, T, E, OE, OE1> Observable<'or, 'sub, T, E> for Switch<OE, OE1>
76where
77    T: 'or,
78    OE: Observable<'or, 'sub, OE1, E>,
79    OE1: Observable<'or, 'sub, T, E>,
80    'sub: 'or,
81{
82    fn subscribe(
83        self,
84        observer: impl Observer<T, E> + NecessarySendSync + 'or,
85    ) -> Subscription<'sub> {
86        subscribe_unsub_after_termination(observer, |observer| {
87            let context = Shared::new(Mutable::new(SwitchContext {
88                on_going_sub: None,
89                completed: false,
90            }));
91            let observer = SwitchObserver {
92                observer: Shared::new(Mutable::new(Some(observer))),
93                context: context.clone(),
94                _marker: PhantomData,
95            };
96            self.source.subscribe(observer) + context
97        })
98    }
99}
100
101struct SwitchContext<'sub> {
102    on_going_sub: Option<Subscription<'sub>>,
103    completed: bool,
104}
105
106impl Disposable for Shared<Mutable<SwitchContext<'_>>> {
107    fn dispose(self) {
108        safe_lock_option_disposable!(dispose: self, on_going_sub);
109    }
110}
111
112struct SwitchObserver<'sub, T, OR> {
113    observer: Shared<Mutable<Option<OR>>>,
114    context: Shared<Mutable<SwitchContext<'sub>>>,
115    _marker: MarkerType<T>,
116}
117
118impl<'or, 'sub, T, E, OR, OE1> Observer<OE1, E> for SwitchObserver<'sub, T, OR>
119where
120    OR: Observer<T, E> + NecessarySendSync + 'or,
121    OE1: Observable<'or, 'sub, T, E>,
122    'sub: 'or,
123{
124    fn on_next(&mut self, value: OE1) {
125        // Use a placeholder subscription.
126        if let Some(on_going_sub) =
127            safe_lock_option!(replace: self.context, on_going_sub, Subscription::default())
128        {
129            on_going_sub.dispose();
130        }
131        let observer = SwitchInnerObserver {
132            observer: self.observer.clone(),
133            context: self.context.clone(),
134        };
135        let sub = value.subscribe(observer);
136        self.context.lock_mut(|mut lock| {
137            if lock.on_going_sub.is_some() {
138                lock.on_going_sub = Some(sub);
139            } else {
140                // already terminated
141            }
142        });
143    }
144
145    fn on_termination(self, termination: Termination<E>) {
146        match termination {
147            Termination::Completed => {
148                self.context.lock_mut(|mut lock| {
149                    lock.completed = true;
150                    if lock.on_going_sub.is_none() {
151                        drop(lock);
152                        safe_lock_option_observer!(on_termination: self.observer, termination);
153                    }
154                });
155            }
156            Termination::Error(_) => {
157                safe_lock_option_observer!(on_termination: self.observer, termination);
158            }
159        }
160    }
161}
162
163struct SwitchInnerObserver<'sub, OR> {
164    observer: Shared<Mutable<Option<OR>>>,
165    context: Shared<Mutable<SwitchContext<'sub>>>,
166}
167
168impl<T, E, OR> Observer<T, E> for SwitchInnerObserver<'_, OR>
169where
170    OR: Observer<T, E>,
171{
172    fn on_next(&mut self, value: T) {
173        safe_lock_option_observer!(on_next: self.observer, value);
174    }
175
176    fn on_termination(self, termination: Termination<E>) {
177        match termination {
178            Termination::Completed => {
179                self.context.lock_mut(|mut lock| {
180                    if lock.completed {
181                        drop(lock);
182                        safe_lock_option_observer!(on_termination: self.observer, termination);
183                    } else if let Some(on_going_sub) = lock.on_going_sub.take() {
184                        drop(lock);
185                        on_going_sub.dispose();
186                    }
187                });
188            }
189            Termination::Error(_) => {
190                safe_lock_option_observer!(on_termination: self.observer, termination);
191            }
192        }
193    }
194}
rx_rust/operators/combining/switch.rs

rx_rust/operators/combining/
switch.rs
