vue组件中setInterval的使用方法

Question

我在每个my-progress中都定义了timer，用来更新view的值，但是控制台显示的值在不断的变化，而view的值还是没有变化，请问怎么办计时器更改视图的值

Vue.component('my-progress', {
    template: '\
            <div class="progress progress-bar-vertical" data-toggle="tooltip" data-placement="top">\
                <div class="progress-bar" role="progressbar" aria-valuenow="0" aria-valuemin="0" aria-valuemax="100" :style="{height: pgvalue}">{{pgvalue}}\
                </div>\
            </div>\
        ',
    data : function(){  

        return {
            pgvalue : '50%',
            intervalid1:'',
        }
    },
    computed:{

        changes : {
            get : function(){
                return this.pgvalue;
            },
            set : function(v){
                this.pgvalue =  v;
            }
        }
    },
    mounted : function(){

        this.todo()     
    },
    beforeDestroy () {

       clearInterval(this.intervalid1)
    },
    methods : {

        todo : function(){          
            this.intervalid1 = setInterval(function(){
                this.changes = ((Math.random() * 100).toFixed(2))+'%';
                console.log (this.changes);
            }, 3000);
        }
    },
})

这里是 link： jsbin.com/safolom

Answer 1

this 没有指向 Vue。尝试

todo: function(){           
    this.intervalid1 = setInterval(function(){
        this.changes = ((Math.random() * 100).toFixed(2))+'%';
        console.log (this.changes);
    }.bind(this), 3000);
}

或

todo: function(){  
    const self = this;          
    this.intervalid1 = setInterval(function(){
        self.changes = ((Math.random() * 100).toFixed(2))+'%';
        console.log (this.changes);
    }, 3000);
}

或

todo: function(){  
    this.intervalid1 = setInterval(() => {
        this.changes = ((Math.random() * 100).toFixed(2))+'%';
        console.log (this.changes);
    }, 3000);
}

见How to access the correct this inside a callback?

Answer 2

检查这个例子：

Vue.component('my-progress-bar',{
 template:
`<div class="progress">
 <div
  class="progress-bar"
  role="progressbar"
  :style="'width: ' + percent+'%;'"
  :aria-valuenow="percent"
  aria-valuemin="0"
  aria-valuemax="100">
  {{ percent }}%
 </div>
</div>`,
 props: { percent: {default: 0} }
});


new Vue({
 el: '#app',
 data: {p: 50},
 created: function() {
  var self = this;
  setInterval(function() {
        if (self.p<100) {
             self.p++;
         }
    }, 100);
 }
});

<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" rel="stylesheet">

<div id='app'>
  <my-progress-bar :percent.sync='p'>
  </my-progress-bar>
  <hr>
  <button @click='p=0' class='btn btn-danger bt-lg btn-block'>
  Reset Bar Progress
  </button>
</div>

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