相反，使用基于道具值的数据或计算属性.Vue JS

Instead, use a data or computed property based on the prop#39;s value. Vue JS(相反，使用基于道具值的数据或计算属性.Vue JS)

问题描述

好吧，我正在尝试在 Vue 中更改变量"的值，但是当我单击按钮时，它们会在控制台中抛出一条消息:

Well, I'm trying to change a value of "variable" in Vue, but when I click on the button they throw a message in console:

[Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "menuOpen"

我不知道如何解决这个问题...

I have no idea how to solve this problem...

我的文件.vue:

<template>
  <button v-on:click="changeValue()">ALTERAR</button>
</template>

<script>

export default {
  name: 'layout',
  props: [ 'menuOpen' ],
  methods: {
    changeValue: function () {
      this.menuOpen = !this.menuOpen
    }
  },
}

</script>

任何人都可以帮助我吗?谢谢

Any one can help me? Thanks

推荐答案

警告很清楚.在您的 changeValue 方法中，您正在更改属性 menuOpen 的值.这将改变组件内部的值，但是如果 parent 组件由于任何原因必须重新渲染，那么无论 inside 的值如何，组件都将被覆盖当前状态在组件之外.

The warning is pretty clear. In your changeValue method you are changing the value of the property, menuOpen. This will change the value internally to the component, but if the parent component has to re-render for any reason, then whatever the value is inside the component will be overwritten with the current state outside the component.

通常，您通过复制值供内部使用来处理此问题.

Typically you handle this by making a copy of the value for internal use.

export default {
  name: 'layout',
  props: [ 'menuOpen' ],
  data(){
      return {
          isOpen: this.menuOpen
      }
  },
  methods: {
    changeValue: function () {
      this.isOpen= !this.isOpen
    }
  },
}

如果您需要将值的更改传达回父级，那么您应该 $emit 更改.

If you need to communicate the change of the value back to the parent, then you should $emit the change.

changeValue: function () {
    this.isOpen= !this.isOpen
    this.$emit('menu-open', this.isOpen)
}

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