TypeError：无法在exports.sendNotification.functions.database.ref.onWrite.event上读取未定义的属性“ curr_uid”

Question

我正在编写一个程序，以便从firebase的Notifications节点内部获取当前用户ID的值。从那里，我想获取其ID存储在Notification节点中的该用户的详细信息。但是我遇到了cannot read property of curr_uid of undefined

的错误

这是我的index.js文件

const functions = require('firebase-functions');
const admin = require ('firebase-admin');
admin.initializeApp (functions.config().firebase);

exports.sendNotification = functions.database.ref('/Notifications/{curr_uid}').onWrite(event =>
    {           

        const curr_uid = event.params.curr_uid;

        console.log ('uid',curr_uid);

            return admin.database().ref('Notifications/{curr_uid}').once('value').then(snapshot =>
            {
                if(snapshot.exists())
                    {
                        const sender_uid = snapshot.val().By;

                        console.log('New notification from ',sender_uid);
                    }   
            });

                const payload = {
                    notification:   {
                                        title: "New Post",
                                        body: "A new post is added",
                                        icon: "default"
                                    }
                                };

                    return admin.database().ref('Tokens').once('value').then(allToken => 
                        {
                            if(allToken.val())
                            {
                                console.log('token available');
                                const token = Object.keys(allToken.val());
                                return admin.messaging().sendToDevice(token,payload);
                            }
                            else
                            {
                                console.log('No token available');

                            }
                        });


    });

当将当前用户ID子节点添加到该curr_uid的Notifications节点时，我希望向所有设备发送推送通知。我想在该curr_uid节点中获取“按”子键和值，以便以后可以使用它通过用户名发送通知。

This is the Notifications Node in my firebase database