如何从云功能触发 FCM 以更新 Firestore 中的特定字段？

Question

我最近编写了一个云函数，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。但正如您在每个案例中的代码中看到的那样，我添加了代码以在案例满足时触发通知，但即使所有切换案例都失败，用户也会收到通知。我真的很困惑这个问题。

为了更好的解释： ServiceStatus有五种类型

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

我希望仅在 ServiceStatus 中更新类型 - 1、3、5 时才向用户发送通知，否则应忽略函数触发器。为此，我编写了一个 switch case，但它并没有像我预期的那样工作，它会触发所有五种类型的通知，即使有两个 case 不满足。

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，您需要比较该字段的值，因为它在此写入操作之前存在和在写入之后存在。

为此，请从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，我还会检查 event.before 和 event.after 是否存在，因为您的云函数也会在文档创建（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，您可以检查是否刚刚为 ServiceStatus 字段指定了一个值，该值应该触发一条消息，并使用一系列 if 语句发送消息，例如

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