RxJS withLatestFrom

將源 Observable 與其他 Observable 組合以創(chuàng)建 Observable 其值是根據(jù)每個值的最新值計算得出的，僅當(dāng) 源發(fā)出。

withLatestFrom<T, R>(...args: any[]):OperatorFunction<T, R>

參量

returns

OperatorFunction<T, R>：最近的預(yù)測值的可觀察值 每個可觀察輸入的值，或來自最新輸入值的數(shù)組 每個輸入都是可觀察的。

描述

只要源 Observable 發(fā)出一個值，它就會 使用該值加上其他輸入的最新值來計算公式 可觀察對象，然后發(fā)出該公式的輸出。

withLatestFrom合并來源 Observable（ 實例）僅在其他情況下具有其他輸入 Observables 的最新值 源發(fā)出一個值，可以選擇使用 project 函數(shù)來確定 要在輸出 Observable 上發(fā)出的值。 所有輸入的觀測值必須 在輸出 Observable 發(fā)出值之前，至少發(fā)出一個值。

例

在每個 click 事件上，發(fā)出帶有最新計時器事件和 click 事件的數(shù)組

import { fromEvent, interval } from 'rxjs';
import { withLatestFrom } from 'rxjs/operators';


const clicks = fromEvent(document, 'click');
const timer = interval(1000);
const result = clicks.pipe(withLatestFrom(timer));
result.subscribe(x => console.log(x));

超載

withLatestFrom(project: (v1: T) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R> withLatestFrom(source2: O2, project: (v1: T, v2: ObservedValueOf<O2>) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R> withLatestFrom(v2: O2, v3: O3, project: (v1: T, v2: ObservedValueOf<O2>, v3: ObservedValueOf<O3>) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R> withLatestFrom(v2: O2, v3: O3, v4: O4, project: (v1: T, v2: ObservedValueOf<O2>, v3: ObservedValueOf<O3>, v4: ObservedValueOf<O4>) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R>

withLatestFrom(v2: O2, v3: O3, v4: O4, v5: O5, project: (v1: T, v2: ObservedValueOf<O2>, v3: ObservedValueOf<O3>, v4: ObservedValueOf<O4>, v5: ObservedValueOf<O5>) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R>

withLatestFrom(v2: O2, v3: O3, v4: O4, v5: O5, v6: O6, project: (v1: T, v2: ObservedValueOf<O2>, v3: ObservedValueOf<O3>, v4: ObservedValueOf<O4>, v5: ObservedValueOf<O5>, v6: ObservedValueOf<O6>) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R>

withLatestFrom(source2: O2): OperatorFunction<T, [T, ObservedValueOf<O2>]>

returns OperatorFunction<T, [T, ObservedValueOf<O2>]>

withLatestFrom(v2: O2, v3: O3): OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>]>

returns OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>]>

withLatestFrom(v2: O2, v3: O3, v4: O4): OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>, ObservedValueOf<O4>]>

returns OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>, ObservedValueOf<O4>]>

withLatestFrom(v2: O2, v3: O3, v4: O4, v5: O5): OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>, ObservedValueOf<O4>, ObservedValueOf<O5>]>

returns OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>, ObservedValueOf<O4>, ObservedValueOf<O5>]>

withLatestFrom(v2: O2, v3: O3, v4: O4, v5: O5, v6: O6): OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>, ObservedValueOf<O4>, ObservedValueOf<O5>, ObservedValueOf<O6>]>

returns OperatorFunction<T, [T, ObservedValueOf<O2>, ObservedValueOf<O3>, ObservedValueOf<O4>, ObservedValueOf<O5>, ObservedValueOf<O6>]>

withLatestFrom(...observables: any[]): OperatorFunction<T, R>

returns OperatorFunction<T, R>

withLatestFrom(array: any[]): OperatorFunction<T, R>

returns OperatorFunction<T, R> withLatestFrom(array: any[], project: (...values: any[]) => R): OperatorFunction<T, R>

returns OperatorFunction<T, R>

也可以看看

• combineLatest