Firebase数据库触发器返回空值

Question

我为数据库触发器创建了Firebase Cloud函数，并成功部署了该函数，但该函数无法检索数据。

exports.newRide = functions.database.ref('/ride/{userid}')
    .onCreate((snapshot, context) => {
      console.log("THIS IS SNAPSHOT");
      console.log(snapshot.val());
      console.log("THIS IS userid");
      myUID = context.params.userid;
      console.log({[myUID] : 1});
      console.log("This is[myUID]")
      console.log([myUID]);
      console.log("This is the wildcardname")
      wildCardValue = context.params.wildCardName
      console.log(wildCardValue);
      return snapshot.val();
);

哪个在控制台日志中返回null或undefined。

2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 null
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 THIS IS userid
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 null
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 { '{userid}': 1 }
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 THIS IS SNAPSHOT parent
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 This is[myUID]
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 [ '{userid}' ]
2020-08-05 16:23:36.276 HKTnewRidedxxxxea8zyc3 This is the wildcardname
2020-08-05 16:23:36.280 HKTnewRidedxxxxea8zyc3 Reference {
2020-08-05 16:23:36.280 HKTnewRidedxxxxea8zyc3 repo:
2020-08-05 16:23:36.280 HKTnewRidedxxxxea8zyc3 Repo {
2020-08-05 16:23:36.280 HKTnewRidedxxxxea8zyc3 repoInfo_:
2020-08-05 16:23:36.280 HKTnewRidedxxxxea8zyc3 RepoInfo {
...

这是我在云功能测试中使用的数据库结构。

{
    "ride": {
        "uid123": {
            "destination": "ChIJJz7FNzUPER8j__MWKHY",
            "distance": "21.1 km",
            "duration": "18 mins",
            "expoPushToken": "ExponentPushToken[Y-YRJKEQU-lngkLAi]",
            "latitude": 1.3291467,
            "longitude": 103.776495,
            "price": 16
        }
    }
}

这是我的package.json文件。

{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "scripts": {
    "serve": "firebase emulators:start --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  },
  "engines": {
    "node": "10"
  },
  "dependencies": {
    "expo-server-sdk": "^3.5.1",
    "firebase-admin": "^8.10.0",
    "firebase-functions": "^3.6.1",
    "node-fetch": "^2.6.0"
  },
  "devDependencies": {
    "firebase-functions-test": "^0.2.0"
  },
  "private": true
}