要防止可观察订阅针对每个发出的值再次运行,可以采取以下方法:
share()
:share()
操作符可以将可观察对象转换为共享的可观察对象,这样多个订阅者可以共享同一个源,并且每个订阅者只会收到一次发出的值。例如:import { Observable } from 'rxjs';
import { share } from 'rxjs/operators';
const observable = new Observable(observer => {
console.log('Observable created');
observer.next('Hello');
observer.next('World');
});
const sharedObservable = observable.pipe(share());
sharedObservable.subscribe(value => console.log('Subscriber 1:', value));
sharedObservable.subscribe(value => console.log('Subscriber 2:', value));
输出结果为:
Observable created
Subscriber 1: Hello
Subscriber 1: World
Subscriber 2: Hello
Subscriber 2: World
publish()
和connect()
:publish()
操作符可以将可观察对象转换为可连接的可观察对象,然后使用connect()
方法手动连接可观察对象。这样可以实现多个订阅者共享同一个源,并且每个订阅者只会收到一次发出的值。例如:import { Observable } from 'rxjs';
import { publish } from 'rxjs/operators';
const observable = new Observable(observer => {
console.log('Observable created');
observer.next('Hello');
observer.next('World');
});
const connectableObservable = observable.pipe(publish());
connectableObservable.subscribe(value => console.log('Subscriber 1:', value));
connectableObservable.subscribe(value => console.log('Subscriber 2:', value));
connectableObservable.connect();
输出结果为:
Observable created
Subscriber 1: Hello
Subscriber 1: World
Subscriber 2: Hello
Subscriber 2: World
shareReplay()
:shareReplay()
操作符可以将可观察对象转换为共享的可观察对象,并且缓存最新的发出的值,以便新的订阅者可以立即收到最新的值。例如:import { Observable } from 'rxjs';
import { shareReplay } from 'rxjs/operators';
const observable = new Observable(observer => {
console.log('Observable created');
observer.next('Hello');
observer.next('World');
});
const sharedReplayObservable = observable.pipe(shareReplay(1));
sharedReplayObservable.subscribe(value => console.log('Subscriber 1:', value));
sharedReplayObservable.subscribe(value => console.log('Subscriber 2:', value));
输出结果为:
Observable created
Subscriber 1: Hello
Subscriber 1: World
Subscriber 2: World
以上是防止可观察订阅针对每个发出的值再次运行的几种方法。在实际应用中,可以根据具体需求选择适合的方法。
领取专属 10元无门槛券
手把手带您无忧上云