How to let vue change the calculated property but not change the selected value of select-H5 Tutorial-php.cn

How to let vue change the calculated property but not change the selected value of select

php中世界最好的语言

Release： 2018-03-27 17:29:32

Original

2268 people have browsed it

This time I will show you how to let vue change the calculated propertypropertybut not change the selected value of select, vue changes the calculated property but does not change the selected value of selectWhat are the precautions , the following is a practical case, let’s take a look.

Let’s start with the code:

//...
<body>
  <p id="qwe">
    <select v-model="selected">
      <option v-for="item in da" :value="item.value">{{item.value}}</option>
    </select>
    <span>{{selected}}</span>
  </p>
  <script>
    var dt = [{
      value: '111',
      label: 'aaa'
    }, {
      value: '222',
      label: 'bbb'
    }, {
      value: '333',
      label: 'ccc'
    }, {
      value: '444',
      label: 'ddd'
    }, {
      value: '555',
      label: 'fff'
    }];
    var vm = new Vue({
      el: '#qwe',
      data: {
        options: [{
          value: '选项1',
          label: '黄金糕'
        }, {
          value: '选项2',
          label: '双皮奶'
        }, {
          value: '选项3',
          label: '蚵仔煎'
        }, {
          value: '选项4',
          label: '龙须面'
        }, {
          value: '选项5',
          label: '北京烤鸭'
        }],
        selected: ''
      },
      computed: {
        da: function () {
          var _self = this;
          return _self.options.filter(function (item) {
            return +item.value.split('')[2] > 2;
          });
        }
      }
    })
  </script>
</body>
</html>

Copy after login

The above code uses vue’s v-for instruction to bind data to generate options, but today we are learning to write When I suddenly discovered a problem, I bound the calculated attribute da to the v-for instruction, and then replaced the source data options. As a result, the calculated attribute da was correct, but the selected attribute did not change. That is to say, the text of the drop-down box on the page has not changed when it is not expanded, as shown below:

Here you can see that the option of the drop-down box has beenupdated, however the selected attribute is not updated synchronously because it caches the last selected value.

I don’t know if the design here is reasonable, because I rarely use it this way.

But if there are problems, they must be solved. Add selected='' to the calculated attribute in computed, and reset the selected attribute every time the dependency is updated.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!