javascript - 获取 Firebase doc.data 未定义

Question

我正在尝试从我的 Firebase 集合中获取数据。当我安慰的时候。 doc.data().name 它返回名称，但是当我尝试将 doc.data().name 分配给变量时，它向我显示未定义的错误。我正在使用 Vuex 和 firebase。

created() {
    firebase.auth().onAuthStateChanged(function(user) {
      if (user) {
        console.log(user.uid);
        firebase.firestore().collection("profiles").doc(user.uid)
          .get()
          .then(function(doc) {
            console.log("Document data:", doc.data().name);  // Getting value from firebase
            this.profile.name = doc.data().name;   // Getting Undefined Here
          })
          .catch(function(error) {
            console.log("Error getting document:", error);
          });
      } else {

      }
    });
  }


data() {
    return {
        profile: {
            name: null
        }
    };
  },

Answer 1

更改此:

          .then(function(doc) {
            console.log("Document data:", doc.data().name);  // Getting value from firebase
            this.profile.name = doc.data().name;   // Getting Undefined Here
          })

进入此:

          .then((doc) => {
            console.log("Document data:", doc.data().name);  // Getting value from firebase
            this.profile.name = doc.data().name;   // Getting Undefined Here
          })

使用文档中的箭头函数:

An arrow function does not have its own this. The this value of the enclosing lexical scope is used; arrow functions follow the normal variable lookup rules. So while searching for this which is not present in current scope, an arrow function ends up finding the this from its enclosing scope