如何从云端函数中触发FCM，以便在防火墙中更新特定的字段？

Question

最近，我编写了一个云函数，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，正如您在我的代码中所看到的，在每一种情况下，我都添加了代码以在情况满足时触发通知，但是用户收到通知，甚至所有的开关情况都失败了。我对这个问题真的很困惑。

更好的解释：ServiceStatus有五种类型

1. Type - 1
2. Type - 2
3. Type - 3
4. Type -4

H 111Type-5H 212G 213

我希望只有在ServiceStatus中更新- 1、3、5类型时才向用户发送通知，否则函数触发器应该被忽略。为此，我编写了一个开关用例，但这不像我预期的那样工作，因为它会触发所有五种类型的通知，尽管两种情况不能满足。

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

如果您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此写操作之前存在的值和在写入后存在的值。

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') : "";

您将注意到，我还会检查event.before和event.after是否存在，因为您的云函数也将在文档创建(此时event.before未定义)和文档删除(此时event.after将未定义)时触发。

现在，使用这两个值，您可以检查ServiceStatus字段是否刚刚被赋予了一个值，该值应该触发一系列if语句发送的消息，如

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