67 lines
1.9 KiB
TypeScript
67 lines
1.9 KiB
TypeScript
/*
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Copyright 2023 New Vector Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import {
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DependencyList,
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Dispatch,
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SetStateAction,
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useCallback,
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useRef,
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useState,
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} from "react";
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/**
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* Hook creating a stateful value that updates automatically whenever the
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* dependencies change. Or equivalently, a version of useMemo that takes its own
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* previous value as an input, and can be updated manually.
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*/
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export const useReactiveState = <T>(
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updateFn: (prevState?: T) => T,
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deps: DependencyList
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): [T, Dispatch<SetStateAction<T>>] => {
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const state = useRef<T>();
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if (state.current === undefined) state.current = updateFn();
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const prevDeps = useRef<DependencyList>();
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// Since we store the state in a ref, we use this counter to force an update
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// when someone calls setState
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const [, setNumUpdates] = useState(0);
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// If this is the first render or the deps have changed, recalculate the state
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if (
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prevDeps.current === undefined ||
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deps.length !== prevDeps.current.length ||
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deps.some((d, i) => d !== prevDeps.current![i])
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) {
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state.current = updateFn(state.current);
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}
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prevDeps.current = deps;
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return [
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state.current,
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useCallback(
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(action) => {
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if (typeof action === "function") {
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state.current = (action as (prevValue: T) => T)(state.current!);
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} else {
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state.current = action;
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}
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setNumUpdates((n) => n + 1); // Force an update
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},
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[setNumUpdates]
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),
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];
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};
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