firestore onSnapshot执行两次 [英] firestore onSnapshot executing twice

问题描述

我的firestore onSnapshot()函数被调用两次.

My firestore onSnapshot() function is being called twice.

let user = firebase.firestore().collection('users').doc(userID).onSnapshot
({                    
    next: (documentSnapshot: firebase.firestore.DocumentSnapshot) =>
    {
         this.userArray.push(documentSnapshot as User);
         console.log(documentSnapshot);
         //here
    },
    error: (firestoreError: firebase.firestore.FirestoreError) =>
    {
         console.log(firestoreError);
         //here
    }
});

我也尝试过在 https://firerefer.google .com/docs/firestore/query-data/listen#detach_a_listener ，在//此处注释中包含user()，但无济于事.

I have also tried subscribing like in https://firebase.google.com/docs/firestore/query-data/listen#detach_a_listener by including user() at the //here comment but to no avail.

我该如何修改，以使该功能仅执行一次，即每次仅推送一个用户对象，而不是两次.

How can I modify such that the function only executes one time, i.e. push only one user object per time instead of twice.

推荐答案

我不知道这是否与您的问题有关.如果有人在使用

I don't know if this is related to your question. If one is using

firebase.firestore.FieldValue.serverTimestamp()

给文档加上时间戳，然后onSnaphot将触发两次.这似乎是因为将新文档添加到数据库时，onSnapshot将触发，但是serverTimestamp尚未运行.几毫秒后，serverTimestamp将运行并更新您的文档=> onSnapshot将再次触发.

to give a document a timestamp, then onSnaphot will fire twice. This seem to be because when you add a new document to your database onSnapshot will fire, but the serverTimestamp has not run yet. After a few milliseconds serverTimestamp will run and update you document => onSnapshot will fire again.

我想在onSnapshot触发之前添加一小段延迟时间(例如0.5秒左右)，但是我找不到执行此操作的方法.

I would like to add a small delay before onSnapshot fires (say 0,5s or so), but I couldn't find the way to do this.

您还可以为onCreate事件创建服务器端功能，我相信这可以解决您的问题.也许您的userArray.push-action更适合在服务器端执行.

You can also make a server side function for onCreate event, I believe that would solve your problem. Maybe your userArray.push-action would be more suitable to execute in server side.

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