Ios 无法读取Firebase函数中null的属性

我正在向订阅Firebase消息中某个主题的用户发送推送通知。一切正常，但在消息发出后，我从

event.data.adminRef

中删除了值，我在Firebase函数日志中得到了此错误消息：

TypeError: Cannot read property 'receiverId' of null
at exports.sendNotification.ref.onWrite.event (/user_code/index.js:24:38)
at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:35:20
at process._tickDomainCallback (internal/process/next_tick.js:129:7)

通知职能：

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
var ref = functions.database.ref('/notificationRequests/{notificationId}')

exports.sendNotification = ref.onWrite(event => {
    var notificationId = event.params.notificationId;
    var notificationRequest = event.data.val();
    console.log(notificationRequest);
    var receiverId = notificationRequest.receiverId;
    var message = notificationRequest.message
    var data = notificationRequest.data

    // The topic name can be optionally prefixed with "/topics/".
    var topic = '/topics/user_' + receiverId;

    // See the "Defining the message payload" section below for details
    // on how to define a message payload.
    var payload = {
      notification: {
       body: message,
       sound: 'default'
      },
      data: { data }
    };

    var options = {
      priority: "high",
      contentAvailable: true
    };

    // Send a message to devices subscribed to the provided topic.
    admin.messaging().sendToTopic(topic, payload, options)
      .then(function(response) {
       // See the MessagingTopicResponse reference documentation for the
       // contents of response.
       console.log("Successfully sent message:", response);
       return event.data.adminRef.remove();
     })
     .catch(function(error) {
       console.log("Error sending message:", error);
     });
});

---

这是什么意思？谢谢

当您在发送消息后删除消息数据时，删除操作（相当于写入空值）会触发函数再次运行，这次是使用空数据。您需要在顶部添加空数据检查，以缩短第二次调用：

if (!notificationRequest) {
  return;
}

您还需要返回由

sendToTopic（）返回的承诺。然后（）

code。这确保了在发送消息和删除数据的异步处理完成之前，您的云功能将保持活动状态

// return added
return admin.messaging().sendToTopic(topic, payload, options)
  .then(function(response) {
   // See the MessagingTopicResponse reference documentation for the
   // contents of response.
   console.log("Successfully sent message:", response);
   return event.data.adminRef.remove();
 })
 .catch(function(error) {
   console.log("Error sending message:", error);
 });

---

当您在发送消息后删除消息数据时，删除操作（相当于写入空值）会触发函数再次运行，这次是使用空数据。您需要在顶部添加空数据检查，以缩短第二次调用：

if (!notificationRequest) {
  return;
}

您还需要返回由

sendToTopic（）返回的承诺。然后（）

code。这确保了在发送消息和删除数据的异步处理完成之前，您的云功能将保持活动状态

// return added
return admin.messaging().sendToTopic(topic, payload, options)
  .then(function(response) {
   // See the MessagingTopicResponse reference documentation for the
   // contents of response.
   console.log("Successfully sent message:", response);
   return event.data.adminRef.remove();
 })
 .catch(function(error) {
   console.log("Error sending message:", error);
 });