VUE2将参数从子节点传递给父节点

Question

如何使用$ emit函数正确地将参数从子节点传递给父节点？在这里我做了什么

HTML

<lista-servizi-gialla :servizi="modello" v-on:centramappa="mappaCenter(x,y,selected)"></lista-servizi-gialla>

零件

template'
<span class="pull-right forward"
 v-on:click="centraNellaMappa(single.x,single.y,single.selected)"></span>',

methods:{
    centraNellaMappa : function(x,y,selected){
        this.$emit('centramappa',[x],[y],[selected]);
     }  
}

父母的功能

mappaCenter : function(x,y,selected){
    alert(x);
}   

'x'参数似乎无法识别

Answer 1

实际上你几乎就在那里,唯一的问题是你用于内联自定义事件处理程序的写作风格.

v-on:centramappa="mappaCenter(x,y,selected)"

vue将在vue实例(this.x...)中查找x,y和所选变量.由于您未在实例中定义它们,因此会抛出错误.
所以你有3个解决方案来解决这个问题.

1. 最简单的一个.您可以像这样传递方法名称.
   v-on:centramappa="mappaCenter"
   vue将自动匹配该方法并为您传递参数.见下面的演示.

Vue.component('lista-servizi-gialla', {
  template: `
<span class="pull-right forward"
 v-on:click="centraNellaMappa(3, 5, true)">
test 
</span>
  `,
  methods:{
    centraNellaMappa : function(x, y, selected) {
      this.$emit('centramappa', [x], [y], [selected]);
    }  
  }
});

new Vue({
  el: '#app',
  methods: {
    mappaCenter: function(x, y, selected){
      //alert(x);
      console.log(`x: ${x}, y: ${y}, selected: ${selected}`);
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.4.2/vue.min.js"></script>
<div id="app">
<lista-servizi-gialla v-on:centramappa="mappaCenter"></lista-servizi-gialla>
</div>

2. 您还可以将参数包装到对象中.Vue提供了一个名为的特殊变量$event,它的值将被设置为您在$emit事件中传递的第一个参数.
   v-on:centramappa="mappaCenter($event)"
   见下面的演示.

Vue.component('lista-servizi-gialla', {
  template: `
<span class="pull-right forward"
 v-on:click="centraNellaMappa(3, 5, true)">
test 
</span>
  `,
  methods:{
    centraNellaMappa : function(x, y, selected) {
      this.$emit('centramappa', {x, y, selected});
    }  
  }
});

new Vue({
  el: '#app',
  methods: {
    mappaCenter: function({ x, y, selected }){
      //alert(x);
      console.log(`x: ${x}, y: ${y}, selected: ${selected}`);
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.4.2/vue.min.js"></script>
<div id="app">
<lista-servizi-gialla v-on:centramappa="mappaCenter($event)"></lista-servizi-gialla>
</div>

3. 如果您坚持mappaCenter以当前形式保留方法,则可以使用JavaScript规范中定义的参数变量.
   v-on:centramappa="mappaCenter(...arguments)"
   或者
   v-on:centramappa="mappaCenter(arguments[0], arguments[1], arguments[2])"
   请参阅下面的演示并查看此答案以获取更多信息.

Vue.component('lista-servizi-gialla', {
  template: `
<span class="pull-right forward"
 v-on:click="centraNellaMappa(3, 5, true)">
test 
</span>
  `,
  methods:{
    centraNellaMappa : function(x, y, selected) {
      this.$emit('centramappa', [x], [y], [selected]);
    }  
  }
});

new Vue({
  el: '#app',
  methods: {
    mappaCenter: function(x, y, selected){
      //alert(x);
      console.log(`x: ${x}, y: ${y}, selected: ${selected}`);
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.4.2/vue.min.js"></script>
<div id="app">
<lista-servizi-gialla v-on:centramappa="mappaCenter(arguments[0], arguments[1], arguments[2])"></lista-servizi-gialla>
</div>