vue3 effect.spec

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目录

原型

观察的对象的变更会同步到原始对象

重复观察相同的原始对象直接返回相同的proxy对象

不会污染原始对象

通过toRaw api可以返回被观察对象的原始对象

shallowReactive

结语

---

1. 定义一个对象original，reactive后返回observed，得到结果两个对象的引用不能相同，observed是可响应的，original不可响应，observed得值跟original相同，从这几个特点来看，我们很容易联想到proxy，对proxy还不熟悉同学可以点proxy

  test('Object', () => {
    const original = { foo: 1 }
    const observed = reactive(original)
    expect(observed).not.toBe(original)
    expect(isReactive(observed)).toBe(true)
    expect(isReactive(original)).toBe(false)
    // get
    expect(observed.foo).toBe(1)
    // has
    expect('foo' in observed).toBe(true)
    // ownKeys
    expect(Object.keys(observed)).toEqual(['foo'])
  })

1. 原型

  test('proto', () => {
    const obj = {}
    const reactiveObj = reactive(obj)
    expect(isReactive(reactiveObj)).toBe(true)
    // read prop of reactiveObject will cause reactiveObj[prop] to be reactive
    // @ts-ignore
    const prototype = reactiveObj['__proto__']
    const otherObj = { data: ['a'] }
    expect(isReactive(otherObj)).toBe(false)
    const reactiveOther = reactive(otherObj)
    expect(isReactive(reactiveOther)).toBe(true)
    expect(reactiveOther.data[0]).toBe('a')
  })

1. 定义一个嵌套对象, reactive后嵌套的属性也可以响应

  test('nested reactives', () => {
    const original = {
      nested: {
        foo: 1
      },
      array: [{ bar: 2 }]
    }
    const observed = reactive(original)
    expect(isReactive(observed.nested)).toBe(true)
    expect(isReactive(observed.array)).toBe(true)
    expect(isReactive(observed.array[0])).toBe(true)
  })

1. 观察的对象的变更会同步到原始对象

  test('observed value should proxy mutations to original (Object)', () => {
    const original: any = { foo: 1 }
    const observed = reactive(original)
    // set
    observed.bar = 1
    expect(observed.bar).toBe(1)
    expect(original.bar).toBe(1)
    // delete
    delete observed.foo
    expect('foo' in observed).toBe(false)
    expect('foo' in original).toBe(false)
  })

1. 给observed设置一个未被观察的值可以响应，看过vue2.x的同学应该都清楚，这个在vue2.x中是不可响应的

test('setting a property with an unobserved value should wrap with reactive', () => {
  const observed = reactive<{ foo?: object }>({})
  const raw = {}
  observed.foo = raw
  expect(observed.foo).not.toBe(raw)
  expect(isReactive(observed.foo)).toBe(true)
})

1. 观察一个已经被observed的observe应该直接返回该observe

test('observing already observed value should return same Proxy', () => {
  const original = { foo: 1 }
  const observed = reactive(original)
  const observed2 = reactive(observed)
  expect(observed2).toBe(observed)
})

1. 重复观察相同的原始对象直接返回相同的proxy对象

test('observing the same value multiple times should return same Proxy', () => {
  const original = { foo: 1 }
  const observed = reactive(original)
  const observed2 = reactive(original)
  expect(observed2).toBe(observed)
})

1. 不会污染原始对象

test('should not pollute original object with Proxies', () => {
  const original: any = { foo: 1 }
  const original2 = { bar: 2 }
  const observed = reactive(original)
  const observed2 = reactive(original2)
  observed.bar = observed2
  expect(observed.bar).toBe(observed2)
  expect(original.bar).toBe(original2)
})

1. 通过toRaw api可以返回被观察对象的原始对象

test('unwrap', () => {
  const original = { foo: 1 }
  const observed = reactive(original)
  expect(toRaw(observed)).toBe(original)
  expect(toRaw(original)).toBe(original)
})

test('should not unwrap Ref', () => {
  const observedNumberRef = reactive(ref(1))
  const observedObjectRef = reactive(ref({ foo: 1 }))

  expect(isRef(observedNumberRef)).toBe(true)
  expect(isRef(observedObjectRef)).toBe(true)
})

test('should unwrap computed refs', () => {
  // readonly
  const a = computed(() => 1)
  // writable
  const b = computed({
    get: () => 1,
    set: () => {}
  })
  const obj = reactive({ a, b })
  // check type
  obj.a + 1
  obj.b + 1
  expect(typeof obj.a).toBe(`number`)
  expect(typeof obj.b).toBe(`number`)
})

1. 不能直接被观察的类型

test('non-observable values', () => {
  const assertValue = (value: any) => {
    reactive(value)
    expect(
      `value cannot be made reactive: ${String(value)}`
    ).toHaveBeenWarnedLast()
  }

  // number
  assertValue(1)
  // string
  assertValue('foo')
  // boolean
  assertValue(false)
  // null
  assertValue(null)
  // undefined
  assertValue(undefined)
  // symbol
  const s = Symbol()
  assertValue(s)

  // built-ins should work and return same value
  const p = Promise.resolve()
  expect(reactive(p)).toBe(p)
  const r = new RegExp('')
  expect(reactive(r)).toBe(r)
  const d = new Date()
  expect(reactive(d)).toBe(d)
})

1. markRaw 可以给将要被观察的数据打上标记，标记原始数据不可被观察

test('markRaw', () => {
  const obj = reactive({
    foo: { a: 1 },
    bar: markRaw({ b: 2 })
  })
  expect(isReactive(obj.foo)).toBe(true)
  expect(isReactive(obj.bar)).toBe(false)
})

1. 被freeze的数据不可观察

test('should not observe frozen objects', () => {
  const obj = reactive({
    foo: Object.freeze({ a: 1 })
  })
  expect(isReactive(obj.foo)).toBe(false)
})

shallowReactive

只为某个对象的私有（第一层）属性创建浅层的响应式代理，不会对“属性的属性”做深层次、递归地响应式代理

1. 属性的属性不会被观察

test('should not make non-reactive properties reactive', () => {
  const props = shallowReactive({ n: { foo: 1 } })
  expect(isReactive(props.n)).toBe(false)
})

1. shallowReactive后的proxy的属性再次被reactive可以被观察

test('should keep reactive properties reactive', () => {
  const props: any = shallowReactive({ n: reactive({ foo: 1 }) })
  props.n = reactive({ foo: 2 })
  expect(isReactive(props.n)).toBe(true)
})

1. iterating 不能被观察

test('should not observe when iterating', () => {
  const shallowSet = shallowReactive(new Set())
  const a = {}
  shallowSet.add(a)

  const spreadA = [...shallowSet][0]
  expect(isReactive(spreadA)).toBe(false)
})

1. get 到的某个属性不能被观察

test('should not get reactive entry', () => {
  const shallowMap = shallowReactive(new Map())
  const a = {}
  const key = 'a'

  shallowMap.set(key, a)

  expect(isReactive(shallowMap.get(key))).toBe(false)
})

1. foreach 不能被观察

test('should not get reactive on foreach', () => {
  const shallowSet = shallowReactive(new Set())
  const a = {}
  shallowSet.add(a)

  shallowSet.forEach(x => expect(isReactive(x)).toBe(false))
})

Vue3中响应数据核心是 reactive ， reactive 中的实现是由 proxy 加 effect 组合，先来看一下 reactive 方法的定义

export function reactive(target: T): UnwrapNestedRefs
export function reactive(target: object) {
  // if trying to observe a readonly proxy, return the readonly version.
  // 如果目标对象是一个只读的响应数据,则直接返回目标对象
  if (target && (target as Target).__v_isReadonly) {
    return target
  }

  // 否则调用  createReactiveObject 创建 observe
  return createReactiveObject(
    target, 
    false,
    mutableHandlers,
    mutableCollectionHandlers
  )
}

createReactiveObject 创建 observe

// Target 目标对象
// isReadonly 是否只读 
// baseHandlers 基本类型的 handlers
// collectionHandlers 主要针对(set、map、weakSet、weakMap)的 handlers
function createReactiveObject(
  target: Target,
  isReadonly: boolean,
  baseHandlers: ProxyHandler,
  collectionHandlers: ProxyHandler
) {
  // 如果不是对象
  if (!isObject(target)) {
    // 在开发模式抛出警告，生产环境直接返回目标对象
    if (__DEV__) {
      console.warn(`value cannot be made reactive: ${String(target)}`)
    }
    return target
  }
  // target is already a Proxy, return it.
  // exception: calling readonly() on a reactive object
  // 如果目标对象已经是个 proxy 直接返回
  if (target.__v_raw && !(isReadonly && target.__v_isReactive)) {
    return target
  }
  // target already has corresponding Proxy
  if (
    hasOwn(target, isReadonly ? ReactiveFlags.readonly : ReactiveFlags.reactive)
  ) {
    return isReadonly ? target.__v_readonly : target.__v_reactive
  }
  // only a whitelist of value types can be observed.

  // 检查目标对象是否能被观察, 不能直接返回
  if (!canObserve(target)) {
    return target
  }

  // 使用 Proxy 创建 observe 
  const observed = new Proxy(
    target,
    collectionTypes.has(target.constructor) ? collectionHandlers : baseHandlers
  )

  // 打上相应标记
  def(
    target,
    isReadonly ? ReactiveFlags.readonly : ReactiveFlags.reactive,
    observed
  )
  return observed
}

// 同时满足3个条即为可以观察的目标对象
// 1. 没有打上__v_skip标记
// 2. 是可以观察的值类型
// 3. 没有被frozen
const canObserve = (value: Target): boolean => {
  return (
    !value.__v_skip &&
    isObservableType(toRawType(value)) &&
    !Object.isFrozen(value)
  )
}

// 可以被观察的值类型
const isObservableType = /*#__PURE__*/ makeMap(
  'Object,Array,Map,Set,WeakMap,WeakSet'
)

结语

看到这里我们大概清楚 reactive 是做为整个响应式的入口，负责处理目标对象是否可观察以及是否已被观察的逻辑，最后使用 Proxy 进行目标对象的代理，对 es6 Proxy 概念清楚的同学应该 Proxy 重点的逻辑处理在 Handlers , 接下来我们就一起去看看各种 Handlers

如果你对 Proxy 还不理解，可以点这里学习