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| import { useMemo } from "react"; | |
| export function useComposedRef<TElement>(handlers: RefHandler<TElement>[]) { | |
| // We actually want the handlers to be the dependency list. | |
| // eslint-disable-next-line react-hooks/exhaustive-deps | |
| return useMemo(() => composeRefs(handlers), handlers); | |
| } | |
| function composeRefs<TElement>( | |
| handlers: RefHandler<TElement>[], | |
| ): React.MutableRefObject<null | TElement> { | |
| let element: null | TElement = null; | |
| return { | |
| get current() { | |
| return element; | |
| }, | |
| set current(value) { | |
| setRefs(value, handlers); | |
| element = value; | |
| }, | |
| }; | |
| } | |
| function setRefs<TElement>( | |
| element: null | TElement, | |
| handlers: RefHandler<TElement>[], | |
| ) { | |
| handlers.forEach((handler) => { | |
| // Ingore falsy handlers to allow syntaxes like: | |
| // | |
| // ```js | |
| // const child = React.Children.only(this.props.children) | |
| // return React.cloneElement(child, { | |
| // ref: ref => setRefs(ref, [this.myRef, child.ref]) | |
| // }) | |
| // ``` | |
| if (handler) { | |
| switch (typeof handler) { | |
| case "function": { | |
| handler(element); | |
| break; | |
| } | |
| case "object": { | |
| handler.current = element; | |
| break; | |
| } | |
| default: | |
| throw new Error( | |
| `Only refs of type function and React.createRef() are supported. Got ${typeof handler}.`, | |
| ); | |
| } | |
| } | |
| }); | |
| } | |
| type RefHandler<TElement> = | |
| | React.RefCallback<null | TElement> | |
| | React.MutableRefObject<null | TElement> | |
| | undefined | |
| | null; |
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