如何在firestore中从云函数触发特定字段更新的FCM

Question

我最近写了一个云函数，当文档中有特定更新时，它会向特定用户发送通知，并且运行良好。但是，正如你在我的代码中看到的那样，在每个案例中，我添加了代码来触发通知，只要案例满足，但用户收到通知，即使所有切换案例都失败了。我对这个问题真的很困惑。

为了得到更好的解释：服务状态有五种类型的

1. 类型-1
2. 类型-2
3. 类型-3
4. 类型-4
5. 类型-5

我希望只有在ServiceStatus中更新了类型-1、3、5时才向用户发送通知，否则应忽略函数触发器。为此，我写了一个switch案例，但它并没有像我预期的那样起作用，它会触发所有五种类型的通知，尽管有两种案例不能满足要求。

我的代码：

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
exports.OrderUpdates = functions.firestore.document('orders/{ServiceID}').onWrite(async (event) =>{
const service_id = event.after.get('ServiceID');
const title = event.after.get('ServiceStatus');
let body;
const fcmToken = event.after.get('FCMToken');
const technician_name = event.after.get('TechnicianName');
switch(title){
case "Service Raised":
body = "Thanks for raising a service request with us. Please wait for sometime our customer care executive will respond to your request";
var message = {
token: fcmToken,
notification: {
title: title,
body: body,
},
"android": {
"notification": {
"channel_id": "order_updates"
}
},
data: {
"Service ID": service_id,
},
}

let response = await admin.messaging().send(message);
console.log(response);
break;
case "Technician Assigned":
body = "Our Technician " + technician_name + " has been assigned to your service request. You can contact him now to proceed further";
var message = {
token: fcmToken,
notification: {
title: title,
body: body,
},
"android": {
"notification": {
"channel_id": "order_updates"
}
},
data: {
"Service ID": service_id,
},
}

let response = await admin.messaging().send(message);
console.log(response);
break;
case "Service Completed":
body = "Your Service request has been successfully completed. Please rate and review our service and help us to serve better. n Thanks for doing business with us..!!";
var message = {
token: fcmToken,
notification: {
title: title,
body: body,
},
"android": {
"notification": {
"channel_id": "order_updates"
}
},
data: {
"Service ID": service_id,
},
}

let response = await admin.messaging().send(message);
console.log(response);
break;
}
});

Answer 1

如果只想在状态字段被主动更改时发送消息，则需要比较该字段在写入操作之前和写入之后的值。

为此，从before和after快照中获取字段值：

const beforeTitle = event.before ? event.before.get('ServiceStatus') : "";
const afterTitle = event.after ? event.after.get('ServiceStatus') : "";

您会注意到，我还检查了event.before和event.after是否存在，因为您的云功能也将在文档创建(此时event.before将未定义(和文档删除(此时event.after将未定义。

现在，使用这两个值，您可以检查ServiceStatus字段是否刚刚给定了一个值，该值应该触发一系列if语句(如(发送的消息

if (afterStatus == "Service Raised" && beforeStatus != "Service Raised") {
... send relevant message
}