将源 Observable 与其他 Observable 组合以创建 Observable 其值是根据每个值的最新值计算得出的，仅当 源发出。

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

参量

returns

OperatorFunction<T, R>：最近的预测值的可观察值 每个可观察输入的值，或来自最新输入值的数组 每个输入都是可观察的。

描述

只要源 Observable 发出一个值，它就会 使用该值加上其他输入的最新值来计算公式 可观察对象，然后发出该公式的输出。

withLatestFrom合并来源 Observable（ 实例）仅在其他情况下具有其他输入 Observables 的最新值 源发出一个值，可以选择使用 project 函数来确定 要在输出 Observable 上发出的值。 所有输入的观测值必须 在输出 Observable 发出值之前，至少发出一个值。

例

在每个 click 事件上，发出带有最新计时器事件和 click 事件的数组

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));

超载

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