javascript - Firebase 触发器功能交替工作

Question

我编写了这个 Firebase 函数，该函数在添加数据时触发，它会汇总子值并更新总值字段。

    export const updateTotalAnswersCounts = functions.database
    .ref('/CurrentGame/answers/{aid}').onWrite((change, context) => {
    var collectionRef = change.after.ref.parent;
    let total = 0;
     collectionRef.once('value',(snapshot)=>{
        console.log('snapshot',snapshot.val())
        snapshot.forEach((childSnapshot)=>{
            if(childSnapshot.val()!=null){
                console.log('childSnapshot',childSnapshot.val())
                total+=Number(childSnapshot.val())
            }
            return false;
        })
        const updates = {}
        updates['/totalAnswersCount'] = total;
        firebase.ref('/CurrentGame').update(updates)

    })

    return true;


});

当我向“answers”节点添加新值时，函数触发器就会工作，然后它会获取所有数字(在这张照片中为 1+2+11)，然后将 TotalAnswersCount 更新为总和 = 14。

此添加操作

addAnswer() {
    let answer = 3;
    let userInfo = {
        uid: this.uid, 
        gid: '1',
        qid: '2',
        aid: '3'
    }
    const answer_ref = firebase.database().ref(`CurrentGame/answers/${answer}`);
    const users_answers_ref = firebase.database().ref(`GameQuestionStats/${this.user.uid}/${userInfo.qid}`);

    // Return the promise from countRef.transaction() so our function
    // waits for this async event to complete before it exits.
    return answer_ref.transaction((current) => {
        return (current || 0) + 1;
    }).then(() => {
        return users_answers_ref.set(userInfo,{merge:true})
    });
}

此 Firebase 功能交替工作

1. 当我第一次加载应用程序时，它会更新节点，但不会进行任何更新。
2. 有时会出现延迟，并在 3-4 秒后更新。
3. 有时它会实时更新并且工作正常。

Answer 1

原因是您必须链接 Promise(因此在每个链接步骤返回一个 Promise)。

以下应该有效:

export const updateTotalAnswersCounts = functions.database
.ref('/CurrentGame/answers/{aid}').onWrite((change, context) => {
    const collectionRef = change.after.ref.parent;
    let total = 0;

    return collectionRef.once('value', (snapshot) => {

        console.log('snapshot', snapshot.val())

        snapshot.forEach((childSnapshot) => {
            if (childSnapshot.val() != null) {
                console.log('childSnapshot', childSnapshot.val())
                total += Number(childSnapshot.val())
            }
        })

    }).then(() => {
        const updates = {}
        updates['/totalAnswersCount'] = total
        return firebase.ref('/CurrentGame').update(updates)
    }).catch(error => {
        console.log(error);
        //Error treatment
    });

});

我建议您观看 Doug Stevenson 关于该主题的视频:

https://www.youtube.com/watch?v=7IkUgCLr5oA&t=515s

https://www.youtube.com/watch?v=652XeeKNHSk

https://www.youtube.com/watch?v=d9GrysWH1Lc&t=4s

请注意，当您不在云函数中返回 promise 时，情况 nbr 2(它有延迟并在 3-4 秒后更新)是一种经典行为。