Question

在开发动态FAQ页面时遇到了这种奇怪的行为，在单击问题后显示答案。

当控制答案打开/关闭的布尔值存储在对象中时，视图会立即更新，并立即显示或隐藏答案。但是，当它存储在列表中时，在以其他方式更新视图之前，不会显示或隐藏答案。

这是显示问题https://jsfiddle.net/masterofginseng/ffqt9n4y/6/

的小提琴

HTML


[13:42:17][MSBuild output] SqlBuild:
[13:42:17][MSBuild output]   Creating a model to represent the project...
[13:42:17][MSBuild output] Done Building Project "D:\BuildAgent\work\9d2a77191c8abcc1\Focal\Focal.sqlproj" (default targets) -- FAILED.

和javascript：

<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>

Answer 1

由于Javascript的限制，Vue无法使用以下语法检测项目中值的更改：

questionarray[2] = !questionarray[2]

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

如上面的链接所述，您必须改为使用splice()：

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

Answer 2

这是因为list-rendering caveats

试试这样：

<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]);
    }
  }
});

以下是jsFiddle

或者像Linus博格回答的一个不那么冗长的版本：

<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变化，而不是在数组中？

2 个答案: