异步函数在Angular中返回ZoneAwarePromise [英] Async function returns ZoneAwarePromise in Angular

问题描述

我有函数 currentUserName()，该函数应返回 name ，但返回ZoneAwarePromise，其中包含具有正确数据的__zone_symbol__value.

I have function currentUserName() that should return name but returns ZoneAwarePromise containing __zone_symbol__value with right data.

currentUserName() {
        var firebaseData = firebase.database().ref('users');
        var userid = this.afAuth.auth.currentUser.uid;

        return firebaseData.orderByKey().once('value').then(function (snapshot) {
            var name;
            snapshot.forEach(function (childSnapshot) {
                if (childSnapshot.key === userid) {
                    name = childSnapshot.val().displayName;
                }
            });
            return name;
        });
    }

函数调用:

this.currentUserName().then(function (snapshot) { return snapshot; }));

推荐答案

为什么不使用承诺?

currentUserName(): Promise<any> {
        var firebaseData = firebase.database().ref('users');
        var userid = this.afAuth.auth.currentUser.uid;

        return firebaseData.orderByKey().once('value').then(function (snapshot) {
            var name;
            snapshot.forEach(function (childSnapshot) {
                if (childSnapshot.key === userid) {
                    name = childSnapshot.val().displayName;
                }
            });

            return name;

}

并这样称呼它

this.currentUserName().then(function(name) { console.log(name) }));

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