如何在承诺回调中更新 Vue 应用程序或组件的属性? [英] How can I update a Vue app's or component's property in a promise call back?

问题描述

我需要如下更新 Firebase 回调中的 Vue 属性，但它不起作用.这段代码

I need to update a Vue property in a Firebase callback as follow, but it's not working. This code

methods: {
    sign_out : function(e) {
        this.item_count = 0
    }
}

有效，但在承诺回调中设置属性时:

works, but when the property is set in a promise callback:

methods: {
  sign_out : function(e) {
  firebase.auth().signOut().then(function() {
      this.item_count = 0
    })
  },

在这种情况下如何设置属性的值?

How can I set a property's value in this case?

推荐答案

回调中的 this 指向错误的对象.有几种方法可以解决这个问题.

Your this in your callback is pointing to the wrong object. There are a few ways you can fix this.

1. 在闭包中捕获this.

methods: {
  sign_out : function(e) {
    var self = this;
    self.item_count = 0
    firebase.auth().signOut().then(function() {
      self.item_count = 0
  })
}

使用粗箭头.

Use a fat arrow.

methods: {
  sign_out : function(e) {
    this.item_count = 0
    firebase.auth().signOut().then(() => this.item_count = 0)
  }
}

使用 bind().

Use bind().

methods: {
  sign_out : function(e) {
    this.item_count = 0
    firebase.auth().signOut().then(function() {
      this.item_count = 0
    }.bind(this))
}

胖箭头还不能在所有现代浏览器中使用，所以只有在编译到 es5 时才使用它们.

Fat arrows will not work in all modern browsers yet, so only use them if you are compiling to es5.

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