observable_combine_changes

The CombineChangesObservable subscribes to two input observables, and emits when either of them emit, even if the other haven’t emitted yet.

It wraps downstream signals into the Change<T> enum, where a value is either:

• JustUpdated - When this value’s changed caused the emission.
• Latest - When this value did not change since the last emission.
• None - When this observable have not emitted yet.

See Also

• CombineLatestObservable - Subscribes to two different observables, and emit the latest of both both values when either of them emits. It only starts emitting once both have emitted at least once.
• ZipObservable - Subscribes to two different observables, and emit both values when both of them emits, pairing up emissions by the order they happened.
• JoinObservable - Subscribes to two different observables, and emit the latest of both values once both of them had completed!

Example

cargo run -p rx_core --example observable_combine_changes_example

let mut greetings_subject = PublishSubject::<&'static str>::default();
let mut count_subject = PublishSubject::<usize>::default();

let mut subscription = combine_changes(greetings_subject.clone(), count_subject.clone())
    .subscribe(PrintObserver::new("combine_changes"));

greetings_subject.next("Hello!");
count_subject.next(10);
count_subject.next(20);
greetings_subject.next("Szia!");
greetings_subject.complete();
count_subject.next(30);
count_subject.complete();
subscription.unsubscribe();

Output:

combine_changes - next: (JustUpdated("Hello!"), None)
combine_changes - next: (Latest("Hello!"), JustUpdated(10))
combine_changes - next: (Latest("Hello!"), JustUpdated(20))
combine_changes - next: (JustUpdated("Szia!"), Latest(20))
combine_changes - next: (Latest("Szia!"), JustUpdated(30))
combine_changes - completed
combine_changes - unsubscribed