Vue 父组件访问子组件的计算属性 [英] Vue parent component access to child component's computed Property

问题描述

在 Vue JS 中，当数组元素(子元素)的计算属性发生更改时，我无法观察数组的更改.

我已经在我编写的示例 JSFiddle 中将问题归结了，因此该示例在逻辑上可能没有意义，但它确实显示了我的问题.

https://jsfiddle.net/trush44/9dvL0jrw/latest/

我有一个包含一系列颜色的父组件.每种颜色都使用子组件呈现.子组件有一个名为IsSelected"的计算属性.当任何数组元素上的IsSelected"计算属性发生更改时，我需要遍历整个数组以查看是否仍然选择了数组中的至少 1 个元素，然后相应地设置 IsAnyCheckboxChecked.

1. 你能帮我理解我是否在做我的计算和观察正确吗?
2. 在父组件的监视中，为什么 this.colors[i].IsSelected即使 IsSelected 在 DOM 中呈现得很好，也返回 undefined?

是否选择了任何颜色?...... {{IsAnyCheckboxChecked}}<父内联模板:colors="ColorList"><div><the-child inline-template :color="element" :key="index" v-for="(element, index) in colors"><div>{{颜色.文本}}<input type="checkbox" v-model="color.Answer"/>IsChecked?......{{IsSelected}}
</the-child>

</父母>

Vue.component('the-child', {道具:['颜色']，计算:{IsSelected: 函数 () {返回 this.color.Answer;}}});Vue.component('the-parent', {道具:['颜色']，手表: {颜色: {处理程序:函数(颜色){var isAnyCheckboxChecked = false;for (var i in this.colors) {//IsSelected 未定义，即使它是孙组件中的计算"属性如果(this.colors[i].IsSelected){isAnyCheckboxChecked = true;休息;}}this.$parent.IsAnyCheckboxChecked = isAnyCheckboxChecked;},深:真实}}});//根视图模型var app = new Vue({el: '#app',数据: {'IsAnyCheckboxChecked':假，'颜色列表':[{'文本':'红色'，'答案':对},{'文本':'蓝色'，'答案':假},{'文本':'绿色'，'答案':假}]}});

解决方案

使用 $refs 直接访问孩子.在 v-for ref 内部变为和数组.因为你的 v-for 是基于 this.color.length 无论如何使用相同的东西来循环 $ref var 中的值.

https://jsfiddle.net/goofballtech/a6Lu4750/19/

for (var i in this.colors) {如果 (this.$refs.childThing[i].IsSelected) {isAnyCheckboxChecked = true;休息;}}

In Vue JS, I'm unable to watch for changes to an array when changes are made within an array element's (child's) computed Property.

I've boiled down the issue in a sample JSFiddle I wrote, so the example may not make sense logically but it does show my issue.

https://jsfiddle.net/trush44/9dvL0jrw/latest/

I have a parent component that holds an array of colors. Each color is rendered using a child component. The child component has a computed Property called 'IsSelected'. When the 'IsSelected' computed Property changes on any array element, I need to loop through the entire array to see if at least 1 element in the array is still selected then set IsAnyCheckboxChecked accordingly.

1. Can you help me understand if I'm doing my computed and watch correctly?
2. In the-parent component's watch, why does this.colors[i].IsSelected return undefined even though IsSelected renders just fine in the DOM?

<div id="app">
  Is any Color Selected?...... {{IsAnyCheckboxChecked}}
  <the-parent inline-template :colors="ColorList">
    <div>
      <the-child inline-template :color="element" :key="index" v-for="(element, index) in colors">
        <div>
          {{color.Text}}
          <input type="checkbox" v-model="color.Answer" />
          IsChecked?......{{IsSelected}}
        </div>
      </the-child>
    </div>
  </the-parent>
</div>

Vue.component('the-child', {        
    props: ['color'],
    computed: {
        IsSelected: function () {
            return this.color.Answer;
        }
    }
});

Vue.component('the-parent', {
    props: ['colors'],
    watch: {
        colors: {
            handler: function (colors) {
                var isAnyCheckboxChecked = false;

                for (var i in this.colors) {
                        // IsSelected is undefined even though it's a 'computed' Property in the-grandchild component
                    if (this.colors[i].IsSelected) { 
                        isAnyCheckboxChecked = true;
                        break;
                    }
                }
                this.$parent.IsAnyCheckboxChecked = isAnyCheckboxChecked;
            },
            deep: true
        }
    }
});

// the root view model
var app = new Vue({
    el: '#app',
    data: {
        'IsAnyCheckboxChecked': false,
        'ColorList': [
            {
                'Text': 'Red',
                'Answer': true
            },
            {
                'Text': 'Blue',
                'Answer': false
            },
            {
                'Text': 'Green',
                'Answer': false
            }
        ]
    }
});

解决方案

use $refs for accessing the child directly. Inside a v-for ref becomes and array. since your v-for is based on this.color.length anyway use the same thing to loop though the value in the $ref var.

https://jsfiddle.net/goofballtech/a6Lu4750/19/

<the-child ref="childThing" inline-template :color="element" :key="index" v-for="(element, index) in colors">

for (var i in this.colors) {

  if (this.$refs.childThing[i].IsSelected) { 
    isAnyCheckboxChecked = true;
    break;
  }
}

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