46 lines
1.6 KiB
TypeScript
46 lines
1.6 KiB
TypeScript
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export interface WaitForHandle {
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/** Stops polling. Safe to call even after `find` has already resolved. */
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cancel(): void;
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}
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/**
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* Polls `find` every `intervalMs` (default 100) until it returns a truthy value, then calls
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* `onFound` with it and stops polling.
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*
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* Needed because a plugin's onLoad can run before every Metro module/component it depends on has
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* actually been required - on a cold app start that's a real race, not an edge case. A one-shot
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* `findByX(...)` lookup at that exact moment can come back undefined and, without a retry, never
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* try again for the rest of the session. `waitFor` checks immediately (so there's no added delay
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* once the target is already registered) and keeps retrying otherwise.
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*
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* Returns a handle whose `cancel()` stops the poll - call it from a plugin's unpatch/onUnload so a
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* pending lookup doesn't keep firing (or apply a patch) after the plugin's been turned off.
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*/
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export function waitFor<T>(find: () => T | null | undefined, onFound: (value: T) => void, intervalMs = 100): WaitForHandle {
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let cancelled = false;
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let timer: ReturnType<typeof setInterval> | undefined;
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const immediate = find();
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if (immediate) {
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onFound(immediate);
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return { cancel() {} };
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}
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timer = setInterval(() => {
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if (cancelled) return;
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const value = find();
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if (value) {
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cancelled = true;
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clearInterval(timer);
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onFound(value);
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}
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}, intervalMs);
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return {
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cancel() {
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cancelled = true;
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if (timer) clearInterval(timer);
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}
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};
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}
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