feat(computed): 实现计算属性缓存优化和调度器支持

- 添加 _dirty 标志位控制计算属性重新执行逻辑 - 在 ReactiveEffect 构造函数中增加调度器参数支持 - 实现计算属性值变更时的依赖触发机制 - 重构 triggerEffects 函数优先处理计算属性依赖 - 新增 EffectScheduler 类型定义统一调度器类型 - 添加 computed-cache.html 示例验证缓存功能
2026-02-08 22:39:34 +08:00
parent 4c60486511
commit c07431db08
3 changed files with 67 additions and 9 deletions
--- a/packages/reactivity/src/computed.ts
+++ b/packages/reactivity/src/computed.ts
@@ -1,20 +1,30 @@
 import { isFunction } from '@vue/shared'
 import { Dep } from './dep'
 import { ReactiveEffect } from './effect'
-import { trackRefValue } from './ref'
+import { trackRefValue, triggerRefValue } from './ref'

 export class ComputedRefImpl<T> {
  public dep?: Dep = undefined
  private _value!: T
  public readonly effect: ReactiveEffect<T>
  public readonly __v_isRef = true
+
+  public _dirty = true //为true时,需要重新执行run方法, 也就是说数据脏了的意思
  constructor(getter) {
-    this.effect = new ReactiveEffect(getter)
+    this.effect = new ReactiveEffect(getter, () => {
+      if (!this._dirty) {
+        this._dirty = true
+        triggerRefValue(this)
+      }
+    })
    this.effect.computed = this
  }
  get value() {
-    trackRefValue(this) //触发依赖
+    trackRefValue(this)
+    if (this._dirty) {
+      this._dirty = false
      this._value = this.effect.run()
+    }
    return this._value
  }
 }
--- a/packages/reactivity/src/effect.ts
+++ b/packages/reactivity/src/effect.ts
@@ -1,6 +1,7 @@
 import { createDep, Dep } from './dep'
 import { isArray } from '@vue/shared'
 import { ComputedRefImpl } from './computed'
+export type EffectScheduler = (...args: any[]) => any

 type KeyToDepMap = Map<any, Dep>
 /**
@@ -21,7 +22,10 @@ export let activeEffect: ReactiveEffect | undefined

 export class ReactiveEffect<T = any> {
  computed?: ComputedRefImpl<T>
-  constructor(public fn: () => T) {}
+  constructor(
+    public fn: () => T,
+    public scheduler: EffectScheduler | null = null
+  ) {}
  run() {
    //当前被激活的effect实例
    activeEffect = this
@@ -78,21 +82,37 @@ export function trigger(target: object, key: unknown, newValue: unknown) {
 }

 /**
- * 依次触发dep中保存的依赖
+ * 触发dep中保存的依赖
 * @param dep
 */
 export function triggerEffects(dep: Dep) {
+  //把dep构建为一个数组
  const effects = isArray(dep) ? dep : [...dep]
-  //依次触发依赖
+  //不再依次触发依赖
+  // for (const effect of effects) {
+  //     triggerEffect(effect)
+  // }
+  //而是先触发所有的计算属性依赖, 再触发所有的非计算属性依赖
  for (const effect of effects) {
+    if (effect.computed) {
      triggerEffect(effect)
    }
  }
+  for (const effect of effects) {
+    if (!effect.computed) {
+      triggerEffect(effect)
+    }
+  }
+}

 /**
 * 触发指定依赖
 * @param effect
 */
 export function triggerEffect(effect: ReactiveEffect) {
+  if (effect.scheduler) {
+    effect.scheduler()
+  } else {
    effect.run()
  }
+}
--- a/packages/vue/examples/reactivity/computed-cache.html
+++ b/packages/vue/examples/reactivity/computed-cache.html
@@ -0,0 +1,28 @@
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Document</title>
+  <script src="../../dist/vue.js"></script>
+</head>
+<body>
+<div id="app"></div>
+</body>
+<script>
+  const { reactive,effect,computed } = Vue
+  const obj=reactive({
+    name:'张三'
+  })
+  const computedObj= computed(()=>{
+    console.log('计算属性执行')
+    return '姓名:'+obj.name
+  })
+  effect(()=>{
+    document.querySelector('#app').innerText=computedObj.value
+    document.querySelector('#app').innerText=computedObj.value
+  })
+  setTimeout(()=>{
+    obj.name='李四'
+  },2000)
+</script>
+</html>