Question

我正在使用onSnapshot在Firestore中收听收藏集。每次我从Python后端添加一些数据时，这些数据都会反映在Firebase控制台中，而不反映在我的UI中。

我正确地检查了我是否在侦听正确的集合，并且我的回调正确，以下是我的代码。当我删除change.type时，querySnapshot首先给我空的更改数据，然后再给我从后端添加的数据。

from google.cloud import firestore

db = firestore.Client.from_service_account_json(CREDENTIALS_FILE)

collection_name = 'mycollection'
collection_ref = db.collection(collection_name)

message = {
 'data': 'testing'
}

collection_ref.add(message)

function subscribe_to_notifs(collection_name) {
 var firestore_db = firebase.firestore();
 var collection_ref = firestore_db.collection(collection_name);

 const handleActivitySubscriptionWithInvocation = countFunctionInvocation(handleActivitySubscription, 1);
 collection_ref.onSnapshot(handleActivitySubscriptionWithInvocation);
}

function handleActivitySubscription(querySnapshot) {
 querySnapshot.docChanges().forEach(function(change) {
   console.log(change.doc.data()); // Here I get the data

   if(change.type === 'added') {
    console.log(change.doc.data()); // Here I get an empty response i.e {}
   }
 });
}

/* 
Firestore onSnapshot() sends initial payload which I don't want.
I only need to listen for updates in a collection
This function will make sure that the `subscription_function` is called 2nd time,
so that we get only the updates from a collection. 
*/
function countFunctionInvocation(subscription_function, invoke_before_execution) {
    var count = 0;
    return function (args) {
        count++;
        if (count <= invoke_before_execution) {
            return true;
        }
        else {
            return subscription_function(args, count);
        }
    };
}

我希望change.doc.data()中有一些数据。可能是什么原因？

注意：最初我的收藏夹中没有文档，当我获取一些数据时，我使用Python Admin SDK将其放入Firestore。

添加了change.type时，onSnapshot返回空的文档更改数据

0 个答案: