vue3-yuanma/packages/reactivity/src/computed.ts

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import { effect, ReactiveEffect, activeReactiveEffectStack } from './effect'
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import { UnwrapNestedRefs, knownRefs } from './ref'
import { isFunction } from '@vue/shared'
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export interface ComputedRef<T> {
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readonly value: UnwrapNestedRefs<T>
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readonly effect: ReactiveEffect
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}
export interface ComputedOptions<T> {
get: () => T
set: (v: T) => void
}
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export function computed<T>(
getterOrOptions: (() => T) | ComputedOptions<T>
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): ComputedRef<T> {
const isReadonly = isFunction(getterOrOptions)
const getter = isReadonly
? (getterOrOptions as (() => T))
: (getterOrOptions as ComputedOptions<T>).get
const setter = isReadonly ? null : (getterOrOptions as ComputedOptions<T>).set
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let dirty: boolean = true
let value: any = undefined
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const runner = effect(getter, {
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lazy: true,
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// mark effect as computed so that it gets priority during trigger
computed: true,
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scheduler: () => {
dirty = true
}
})
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const computedValue = {
// expose effect so computed can be stopped
effect: runner,
get value() {
if (dirty) {
value = runner()
dirty = false
}
// When computed effects are accessed in a parent effect, the parent
// should track all the dependencies the computed property has tracked.
// This should also apply for chained computed properties.
trackChildRun(runner)
return value
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},
set value(newValue) {
if (setter) {
setter(newValue)
} else {
// TODO warn attempting to mutate readonly computed value
}
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}
}
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knownRefs.add(computedValue)
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return computedValue
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}
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function trackChildRun(childRunner: ReactiveEffect) {
const parentRunner =
activeReactiveEffectStack[activeReactiveEffectStack.length - 1]
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if (parentRunner) {
for (let i = 0; i < childRunner.deps.length; i++) {
const dep = childRunner.deps[i]
if (!dep.has(parentRunner)) {
dep.add(parentRunner)
parentRunner.deps.push(dep)
}
}
}
}