ReferenceError：未定义上下文

Question

我正在尝试使用 node.js 和 firebase 函数创建一个 sendNotification 函数，但不幸的是我目前被卡住了。我从来没有收到发件人的通知，当我查看 Firebase 函数日志时，我看到一个错误提示

ReferenceError: context is not defined
at exports.sendNotification.functions.database.ref.onWrite.event (/user_code/index.js:9:32)
at Object.<anonymous> (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:112:27)
at next (native)
at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:28:71
at __awaiter (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:24:12)
at cloudFunction (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:82:36)
at /var/tmp/worker/worker.js:700:26
at process._tickDomainCallback (internal/process/next_tick.js:135:7)

这是我的代码 index.js 代码

`const functions = require('firebase-functions');
 const admin = require('firebase-admin');
 admin.initializeApp(functions.config().firebase);
 exports.sendNotification = functions.database.ref('notifications/{user_id}').onWrite(event => {

const user_id = context.params.user_id;
const notification_id = context.params.notification_id;

console.log('We have notification from: ', user_id);

if (!event.val()) {
    return console.log('A Notification has been deleted from the database: ', notification_id);
}

const fromUser = admin.database().ref(`/Users/${user_id}/device_token`).once('value');

return fromUser.then(result => {

    const token_id = result.val();

    const payload = {
        notification: {
            title: "Friend Request",
            body: "You've received a Friend Request",
            icon: "default"
        }
    };

    return admin.messaging().sendToDevice(token_id , payload).then(response => {

        console.log('This was the notification feature');

    });

});

});

我不知道这里的错误在哪里，谁能告诉我错误在哪里，我该如何解决？

Answer 1

在@PeterHaddad 的帮助下，我设法解决了自己的问题。我阅读了他发布的链接，并更改了一些代码。这里是

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

exports.sendNotification = functions.database.ref('notifications/{user_id}').onWrite((change, context) => {

const user_id = context.params.user_id;
const notification_id = context.params.notification_id;

console.log('We have notification from: ', user_id);

if (!change.after.val()) {
    return console.log('A Notification has been deleted from the database: ', notification_id);
}

const fromUser = admin.database().ref(`/Users/${user_id}/device_token`).once('value');

return fromUser.then(result => {

    const token_id = result.val();

    const payload = {
        notification: {
            title: "Friend Request",
            body: "You've received a Friend Request",
            icon: "default"
        }
    };

    return admin.messaging().sendToDevice(token_id , payload).then(response => {

        console.log('This was the notification feature');

    });

});

});

Answer 2

改成这样：

exports.sendNotification = functions.database.ref('notifications/{user_id}').onWrite((change,context) => {

const user_id = context.params.user_id;

});

onWrite 有两个参数change 和context。您使用context 访问通配符示例user_id。

更多信息在这里：

https://firebase.google.com/docs/functions/beta-v1-diff