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42 lines
1.2 KiB
42 lines
1.2 KiB
import {IDisposableOwner, Observable} from 'grainjs';
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export interface PausableObservable<T> extends Observable<T> {
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pause(shouldPause?: boolean): void;
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}
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/**
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* Creates and returns an `Observable` that can be paused, effectively causing all
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* calls to `set` to become noops until unpaused, at which point the last value
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* passed to set, if any, will be applied.
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*
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* NOTE: It's only advisable to use this when there are no other alternatives; pausing
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* updates and notifications to subscribers increases the chances of introducing bugs.
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*/
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export function createPausableObs<T>(
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owner: IDisposableOwner|null,
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value: T,
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): PausableObservable<T> {
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let _isPaused = false;
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let _lastValue: T | undefined = undefined;
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const obs = Observable.create<T>(owner, value);
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const set = Symbol('set');
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return Object.assign(obs, {
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pause(shouldPause: boolean = true) {
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_isPaused = shouldPause;
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if (shouldPause) {
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_lastValue = undefined;
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} else if (_lastValue) {
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obs.set(_lastValue);
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_lastValue = undefined;
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}
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},
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[set]: obs.set,
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set(val: T) {
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_lastValue = val;
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if (_isPaused) { return; }
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this[set](val);
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}
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});
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}
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