Immer 数据未在 Vue 中更新

Question

我正在尝试将 Immer 与 Vue 结合使用。看起来状态正在更新，但 Vue 没有更新 UI

// immutable.js
import produce, { applyPatches } from "immer"

let undo_buffer = []
export var state = { items: [] }
const handle_add_patch = (patch, inverse_patches) => {
  console.log("Inverse Patches: ", inverse_patches)
  undo_buffer.push(inverse_patches)
}
export const add_item = (item_name) => {
  console.log("Starting add_item call")
  const next_state = produce(
    state,
    draft => {
      draft.items.push({ name: item_name })
    },
    handle_add_patch
  )
  console.log("next state: ", next_state)
  state = next_state
}
export const undo = () => {
  const undo_patch = undo_buffer.pop()
  if (!undo_patch) return
  let new_state = applyPatches(state, undo_patch)
  console.log("New State: ", new_state)
  state = new_state
}

<!-- item_list.Vue -->
<template>
  <div>
    <button @click.prevent="add_item()">Add Item</button>
      {{ items }}
    <button @click.prevent="undo()">Undo</button>
  </div>
</template>
<script>
import * as immutable from './immutable.js'
export default {
  computed: {
    items: function(){ return immutable.state.items }
  },
  methods: {
    add_item(){
      console.log("State Before: ", immutable.state)
      immutable.add_item("Hello")
      console.log("State After: ", immutable.state)
    },
    undo(){
      console.log("State Before: ", immutable.state)
      immutable.undo()
      console.log("State After: ", immutable.state)
    }
  }
}
</script>

console.log显示items数组正在变化，但是Vue模板中的items只是显示一个空数组。我怎样才能使它在 Vue 中可见？

Answer 1

计算的属性被缓存，并且在关联的组件数据更改之前不会重新计算它们。由于 Immer 对象不是组件的一部分，因此永远不会发生重新计算。

缓存可以通过使用 getter 方法而不是计算属性:

来防止

{{ getItems() }}

...

methods: {
  getItems: () => immutable.state.items
  addItem() {
    immutable.add_item("Hello");
    this.$forceUpdate();
  }
}

更直接的方法是强制重新计算属性：

data() {
  return { _itemsDirtyFlag: 0 }
},
computed: {
  items: {
    get() {
      this._itemsDirtyFlag; // associate it with this computed property
      return immutable.state.items;
    }
},
methods: {
  updateItems() {
    this._itemsDirtyFlag++;
  },
  addItem() {
    immutable.add_item("Hello");
    this.updateItems();
  }
}

vue-recomputed 使用了一种使用 Vue.util.defineReactive 内部的类似方法。

Answer 2

此问题与 Immer 无关。 vuejs 缓存计算属性，因此它们不会在您的数据更新时更新。 https://vuejs.org/v2/guide/computed.html#Computed-Caching-vs-Methods

的 vuejs 文档中清楚地提到了这一点

Instead of a computed property, we can define the same function as a method. For the end result, the two approaches are indeed exactly the same. However, the difference is that computed properties are cached based on their reactive dependencies. A computed property will only re-evaluate when some of its reactive dependencies have changed.

由于 Immer 不是反应性依赖项，因此计算的属性再也不会运行s。

解决方案是将计算的属性更改为方法。这样它就不会被缓存，并且该方法每次都会运行更新值。

Immer 数据未在 Vue 中更新

Immer data not updating in Vue

javascript

vue.js

immer.js