显示来自 promise firebase 的数据

Question

我有这样的服务

async getBirthdays() {
    const user = await this.authSP.getUserInfo();
    let bdays = [];
    return await new Promise<any>((resolve) => {
    this.angularFire.database.ref("birthdays").orderByChild("creator_user_id").equalTo(user.uid).once("value", (snapshot) => {
        snapshot.forEach(function (childSnapshot) {
          const value = childSnapshot.val();
          value.$key = childSnapshot.key;
          bdays.push(value);
        });
    });

    resolve(bdays);

    });
}

这个承诺返回这个对象数组

在我的组件中，我只是尝试显示头像值：

this.birthdays = await this.birthdaySP.getBirthdays().then(res => {
  var data = res.map(t=>t.avatar);
  console.log(data);
});

但是console.log(data)返回一个空数组。

感谢任何帮助

Answer 1

现在您在once() 回调运行之前调用resolve(bdays)，这意味着bdays 只是一个空数组。

对resolve() 的调用需要在bdays 的回调中包含数据：

async getBirthdays() {
    const user = await this.authSP.getUserInfo();
    let bdays = [];
    return await new Promise<any>((resolve) => {
        this.angularFire.database.ref("birthdays").orderByChild("creator_user_id").equalTo(user.uid).once("value", (snapshot) => {
            snapshot.forEach(function (childSnapshot) {
              const value = childSnapshot.val();
              value.$key = childSnapshot.key;
              bdays.push(value);
            });
            resolve(bdays);
        });    
    });
}

Answer 2

请您尝试以下方法：

this.birthdaySP.getBirthdays().then(res => {
  this.birthdays = res.map(t=>t.avatar);
});