Firebase Cloud Functions在创建实时数据库时获取数据

Question

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

exports.sendNotification = functions.database.ref('/messages/diyetisyen/{uname}/{msgid}/message')
.onCreate((snapshot, context) => {

let message = snapshot.val();
let uname = context.params.uname;
let root = snapshot.ref.root;
let token = root.child('/users/' + uname + '/token').ref.token;

let payload = {
  data: {
    custom_notification: JSON.stringify({
      body: message + '',
      title: 'aaaa'

    })
  }
};
let options = { priority: "high" };


return admin
  .messaging()
  .sendToDevice(token, payload, options);
  });

我无法在/users/{uname}/token上获取令牌-

错误：提供给sendToDevice（）的注册令牌必须是非空字符串或非空数组。在FirebaseMessagingeror。FirebaseError[作为构造函数]（/srv/node_modules/firebase admin/lib/utils/error.js:42:28）位于FirebaseMessagingError。在新FirebaseMessagingError（/srv/node_modules/firebase admin/lib/utils/error.js:88:28）的消息传递中，使用prefixedFreebaseError[作为构造函数]（/srv/node_modules/firebase admin/lib/utils/error.js:253:16）。在messaging上验证RegistrationTokenStype（/srv/node_modules/firebase admin/lib/messaging/messaging.js:911:19）。导出时发送到设备（/srv/node_modules/firebase admin/lib/messaging/messaging.js:532:14）。发送通知。功能。数据库参考cloudFunctionNewSignature（/srv/node_modules/firebase functions/lib/cloud functions.js:120:23）中的onCreate（/srv/index.js:28:5）和/worker/worker。js:825:24在过程中_tickDomainCallback（内部/process/next_tick.js:229:7）

Answer 1

您无法通过执行操作获取数据库节点的值

let token = root.child('/users/' + uname + '/token').ref.token;

您需要使用参考的once（）方法查询数据库，这是异步的。

这意味着您必须按如下方式修改代码：

exports.sendNotification = functions.database.ref('/messages/diyetisyen/{uname}/{msgid}/message')
.onCreate((snapshot, context) => {

    let message = snapshot.val();
    let uname = context.params.uname;
    let root = snapshot.ref.root;
    let tokenRef = root.child('/users/' + uname + '/token').ref;

    let payload = {
       data: {
         custom_notification: JSON.stringify({
           body: message + '',
           title: 'aaaa'   
         })
       }
     };

     let options = { priority: "high" };

     return tokenRef.once('value')
     .then(dataSnapshot => {
       const data = dataSnapshot.val();
       const token = data.token;   //Here I make the assumption the token is at '/users/' + uname + '/token/token'. You may adapt it as required

       return admin
       .messaging()
       .sendToDevice(token, payload, options);
     }); 
});