无法读取未定义的属性"user_id" [英] Cannot read property 'user_id' of undefined
问题描述
我想通过Firebase云功能将设备发送到设备推送通知.我正在编写node.js脚本
I want to send device to device push notification through firebase cloud functions. I am writing node.js script
exports.sendNotification = functions.database.ref('/messages/{user_id}/{rec_user_id}').onWrite((event) => {
const sender_user_id = event.params.user_id;
const receiver_user_id = event.params.rec_user_id;
console.log('We have a notification from : '+ sender_user_id+ " | Receiced by " + receiver_user_id);
return;
});
在Firebase云上部署功能后,出现错误
After deploying function on firebase cloud i got an error
TypeError: Cannot read property 'user_id' of undefined
完整的错误日志是:
TypeError: Cannot read property 'user_id' of undefined
at exports.sendNotification.functions.database.ref.onWrite.event (/user_code/index.js:28:40)
at Object.<anonymous> (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:112:27)
at next (native)
at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:28:71
at __awaiter (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:24:12)
at cloudFunction (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:82:36)
at /var/tmp/worker/worker.js:700:26
at process._tickDomainCallback (internal/process/next_tick.js:135:7)
我从此处得到了答案
I got an answer from here
它工作正常,但是当我使用
It was working fine, but when i used
if(!event.data.val()){
return console.log('A Notification has been deleted from the database : ', sender_user_id);
}
Firebase日志再次开始向我显示一条错误消息
Firebase log again start to give me an error message saying
Cannot read property 'val' of undefined
如何摆脱这些错误? 预先感谢
How to get rid of these errors ? Thanks in advance
推荐答案
关于val()
,您需要执行以下操作:
Regarding val()
you need to do the following:
exports.sendNotification = functions.database.ref('/messages/{user_id}/{rec_user_id}').onWrite((change,context) => {
const afterData=change.after.val();
});
由于您使用的是onWrite()
,因此数据参数应该为change
,它具有before
和after
属性,它们每个都是具有以下方法的DataSnapshot
:
Since you are using onWrite()
then the data parameter should be change
, which has the before
and after
properties, each of these is a DataSnapshot
that has the following methods:
https://firebase.google.com/docs /reference/admin/node/admin.database.DataSnapshot
也供参考:
https://firebase.google.com/docs/reference/functions /functions.Change
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