为什么 v-show 和 v-if 会立即响应对象中的布尔值变化，而不是数组中的变化？

Question

在开发动态常见问题解答页面时遇到了这种奇怪的行为，该页面在单击问题后显示答案。

当控制答案 opening/closing 的布尔值存储在对象中时，视图会立即更新，答案会立即显示或隐藏。但是，当它存储在列表中时，直到以其他方式更新视图时，才会显示或隐藏答案。

这是一个 fiddle 显示问题 https://jsfiddle.net/masterofginseng/ffqt9n4y/6/

HTML

<script src="https://npmcdn.com/vue/dist/vue.js"></script>
<div id="faq">
  <div>This responds immediately</div>
  <hr>
  <div v-for="questionObj in questions1">
    <div style="cursor: pointer;" @click="questionObj.open = !questionObj.open">
      {{ questionObj.question }}
    </div>
    <div style="color: blue;" v-show="questionObj.open">{{ questionObj.answer }}</div>
  </div>
  <br>
  <br>
  <div>This doesn't respond until the view is updated in some other way (ex. by clicking on one of the questions above)</div>
  <hr>
  <div v-for="questionarray in questions2">
    <div style="cursor: pointer;" @click="questionarray[2] = !questionarray[2]">
      {{ questionarray[0] }}
    </div>
    <div style="color: blue;" v-show="questionarray[2]">{{ questionarray[1] }}</div>
  </div>
</div>

和javascript：

new Vue({
  el: "#faq",
  data: {
    questions1: [{
      question: "How big is it?",
      answer: "very big",
      open: false
    }, {
      question: "How small is it?",
      answer: "very small",
      open: false
    }],
    questions2: [
      ["How big is it?", "very big", false],
      ["How small is it?", "very small", false]
    ]
  }
});

Answer 1

由于 Javascript 中的限制，Vue 无法使用此语法检测项目中值的更改：

questionarray[2] = !questionarray[2]

看这里：https://vuejs.org/v2/guide/list.html#Array-Change-Detection

如上面 link 中所述，您必须改用 splice()：

questionarray.splice(2, 1, !questionarray[2])

Answer 2

这是因为list-rendering caveats

这样试试：

<script src="https://npmcdn.com/vue/dist/vue.js"></script>
<div id="faq">
  <div>This responds immediately</div>
  <hr>
  <div v-for="questionObj in questions1">
    <div style="cursor: pointer;" @click="questionObj.open = !questionObj.open">
      {{ questionObj.question }}
    </div>
    <div style="color: blue;" v-show="questionObj.open">{{ questionObj.answer }}</div>
  </div>
  <br>
  <br>
  <div>This doesn't respond until the view is updated in some other way (ex. by clicking on one of the questions above)</div>
  <hr>
  <div v-for="questionarray in questions2">
    <div style="cursor: pointer;" @click="myMethod(questionarray)">
      {{ questionarray[0] }}
    </div>
    <div style="color: blue;" v-show="questionarray[2]">{{ questionarray[1] }}</div>
  </div>
</div>

脚本

new Vue({
  el: "#faq",
  data: {
    questions1: [{
      question: "How big is it?",
      answer: "very big",
      open: false
    }, {
      question: "How small is it?",
      answer: "very small",
      open: false
    }],
    questions2: [
      ["How big is it?", "very big", false],
      ["How small is it?", "very small", false]
    ]
  },
  methods:{
      myMethod(questionArray){
        this.$set(questionArray, 2, !questionArray[2]);
    }
  }
});

这是jsFiddle

或者 Linus borg 回答的更简洁的版本：

<script src="https://npmcdn.com/vue/dist/vue.js"></script>
<div id="faq">
  <div>This responds immediately</div>
  <hr>
  <div v-for="questionObj in questions1">
    <div style="cursor: pointer;" @click="questionObj.open = !questionObj.open">
      {{ questionObj.question }}
    </div>
    <div style="color: blue;" v-show="questionObj.open">{{ questionObj.answer }}</div>
  </div>
  <br>
  <br>
  <div>This doesn't respond until the view is updated in some other way (ex. by clicking on one of the questions above)</div>
  <hr>
  <div v-for="questionarray in questions2">
    <div style="cursor: pointer;" @click="questionarray.splice(2, 1, !questionarray[2])">
      {{ questionarray[0] }}
    </div>
    <div style="color: blue;" v-show="questionarray[2]">{{ questionarray[1] }}</div>
  </div>
</div>

为什么 v-show 和 v-if 会立即响应对象中的布尔值变化，而不是数组中的变化？

Why does v-show and v-if respond immediately to boolean changes in objects, but not in arrays?

javascript

frontend

vue.js

vuejs2