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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 | 2x 2x 2x 9x 9x 9x 9x 9x 9x 4x 9x 5x 5x 14x | import { type DependencyList, useEffect, useRef } from 'react'
import type { Reaction } from 'watch-state'
import { Compute } from 'watch-state'
/**
* Creates a `Compute` instance that can be passed as a static prop to child components.
* Reactivity is activated only in components that call `useWatch` on the Observable.
* This pattern optimizes re-renders: parent components don't re-render when computed values change.
*
* @template T - The type of the computed value
* @param watcher - A function that returns the computed value. This function can access reactive `State` or `Compute` instances.
* @param deps - Optional dependency array that triggers recomputation when values change. Use this for props or external values that should trigger an update.
* @returns A `Compute` instance containing the computed value.
*
* @example
* ```tsx
* // Basic usage //
*
* import { State } from 'watch-state'
* import { useWatch, useNewCompute } from '@watch-state/react'
*
* const $name = new State('Mike')
* const $surname = new State('Deight')
*
* const Parent = () => {
* const $fullName = useNewCompute(() => {
* return `${$name.value} ${$surname.value[0]}.`
* })
*
* return <Child $fullName={$fullName} />
* }
*
* const Child = ({ $fullName }) => {
* const fullName = useWatch($fullName)
*
* return <div>{fullName}</div>
* }
* ```
*
* @example
* ```tsx
* // With dependencies //
*
* import { State } from 'watch-state'
* import { useWatch, useNewCompute } from '@watch-state/react'
*
* const $name = new State('Mike')
*
* const Parent = ({ surname }) => {
* const $fullName = useNewCompute(() => {
* return `${$name.value} ${surname[0]}.`
* }, [surname])
*
* return <Child $fullName={$fullName} />
* }
*
* const Child = ({ $fullName }) => {
* const fullName = useWatch($fullName)
*
* return <div>{fullName}</div>
* }
* ```
*/
export function useNewCompute <T> (watcher: Reaction<T>, deps?: DependencyList) {
const result = useRef<Compute<T>>()
const watcherRef = useRef(watcher)
const updateRef = useRef(false)
watcherRef.current = watcher
useEffect(() => {
if (deps && updateRef.current) {
result.current.update()
}
}, deps)
useEffect(() => {
updateRef.current = true
return () => result.current.destroy()
}, [])
return result.current || (result.current = new Compute(() => watcherRef.current(), true))
}
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