javascript - Vuejs Es6 类反应性

Question

我正在尝试将 vuejs 中的计算属性关联到 es6 类。我的 Vue 实例如下所示：

...
props: ['customClass'],
computed: {
    localClass: {
         get() {
             return this.customClass
         },
         set (value) {
             console.log("changed")
         }
     }
 }
 ...

我的课看起来像这样

class CustomClass {
    constructor () {
        this.selected = false
    }
}

如果我尝试做这样的事情：

this.localClass.selected = true

但是 setter 从来没有被调用过，就像失去了反应一样，我不明白为什么。

我也尝试：

Vue.set(this.localClass, 'selected', true)

我将 customClass 作为道具传递，但即使直接在组件中创建新实例也不会改变结果。

在 vuejs 文档中，我不记得有一节讨论过 es6 类中的反应性问题，所以我想知道是否有人知道为什么以及如何使我的类具有反应性。

提前致谢

Answer 1

计算属性的设置器，例如myComputedProperty，在您分配给该属性时触发（例如this.myComputedProperty = {something: 'else'}.

您可能正在寻找的是watcher，更具体地说，是带有 的 watcherdeep: true，例如：

watch: {
  localClass: {
    deep: true,
    handler() {
      out.innerHTML += "watched!";
    }
  }
},

演示如下。

class CustomClass {
  constructor() {
    this.selected = false
  }
}
Vue.component('custom', {
  template: '#custom',
  props: ['customClass'],
  computed: {
    localClass: {
      get() {
        return this.customClass
      },
      set(value) {
        out.innerHTML += "changed!\n";
      }
    }
  },
  watch: {
    localClass: {
      deep: true,
      handler() {
        out.innerHTML += "watched!\n";
      }
    }
  },
  methods: {
    assignToSelected() {
      this.localClass.selected = true
    },
    assignToLocalClass() {
      this.localClass = {
        selected: true
      }
    }
  }
});
new Vue({
  el: '#app',
  data: {
    test: new CustomClass()
  },
})

#out { background: black; color: gray; }
span { font-size: x-small; font-family: verdana }

<script src="https://unpkg.com/vue"></script>

<template id="custom">
  <div>
    {{ localClass }}
    <br>
    <button @click="assignToSelected">assignToSelected</button>
    <span>Note: will trigger "watched!" just once, because, since the value is hardcoded in the method (see code) subsequent clicks won't modify the value.</span>
    <br><br>
    <button @click="assignToLocalClass">assignToLocalClass</button>
    <span>Note: assignToLocalClass() will trigger the computed setter, but wont trigger the watcher because the computed setter currently sets nothing, so nothing changed for the watcher to trigger.</span>
  </div>
</template>

<div id="app">
  <custom :custom-class="test"></custom>
</div>

<pre id="out"></pre>