Firebase CloudFunctions: Querying Nodes

问题

I am exploring Cloud Functions with FCM to do a push notification to my iOS app device. I have the following structure and I am listening for people who registered to an event. I want to extract the eventHost so that I can go to my users node to find the userUID and eventually his deviceID, and send a push notification to him.

{
  "events" : {
    "XXX" : {
      "eventHost" : "YYY", //<-- How do I get this node?
      "eventID" : "XXX",
      "registered" : {  //<-- Listening for this node
        "ASKDJHAIUCHA" : {
          "name" : "Emma Watson",
          "userUID" : "ASKDJHAIUCHA" 
        }
      },
    },

  },

  "users" : {
    "YYY" : {
      "deviceID" : "1234456",
      "name" : "Andrew Garfield",
      "userUID" : "YYY"
    },
  }
}

My code for the Cloud Functions as such so far:

exports.sendNotification = functions.database.ref('/events/{eventId}/registered')
    .onWrite(event => {
      const register = event.data.val();
      const eventHost = functions.database.ref('/events/' + event.params.eventId + '/eventHost')
      console.log('sendNotifications', eventHost);

      const payload = {
        notification: {
            title: "Event Registration",
            body: "Someone registered to your event!"
        }
      };

      const options = {
        priority: "high"
      };

      return admin.messaging().sendToDevice("theDeviceID", payload, options)

    });

And my Swift portion when adding value into the database is as such:

@IBAction func registerButtonDidTap(_ sender: Any) {

        let personDict = [FIRConstants.UserInfo.Name: user.userName,
                          FIRConstants.UserInfo.UserUID: user.userUID]
        let registerPerson = [user.userUID!: personDict as AnyObject] as [String: AnyObject]
        let values = ["registered": registerPerson]

        FIRHelperClient.sharedInstance.checkIfEventHasRegistrants(ref, event.eventID!) { (has, error) in
            if let error = error {
                print(error.localizedDescription)
            } else {
                if let has = has {
                    if has {
                        self.ref.child("events").child(self.event.eventID!).child("registered").updateChildValues(registerPerson)

                    } else {
                        self.ref.child("events").child(self.event.eventID!).updateChildValues(values)

                    }
                }
            }
        }
    }

My cloud functions is definitely not complete as currently I am hardcoding theDeviceID. As I am pretty inexperience with Node.js and am trying to write both the iOS code in Swift and the server side code, so pls pardon me if this question is elementary. Some advice here would be helpful, thanks.

回答1:

You'll need to read the host, which your code currently doesn't do.

exports.sendNotification = functions.database.ref('/events/{eventId}/registered')
    .onWrite(event => {
      const register = event.data.val();
      const eventHostRef = functions.database.ref('/events/' + event.params.eventId + '/eventHost')
      return eventHostRef.once('value', (eventHostSnapshot) => {
        const eventHost = eventHostSnapshot.val();
        console.log('sendNotifications', eventHost);

        const payload = {
          notification: {
            title: "Event Registration",
            body: "Someone registered to your event!"
          }
        };

        const options = {
          priority: "high"
        };

        return admin.messaging().sendToDevice("theDeviceID", payload, options)
      });
    });

I highly recommend that you spend some time learning how to interact with the Firebase Database through JavaScript before continuing though. This doesn't have to be through Cloud Functions. You could also use the Firebase Database Admin SDK from Node.js on your client or take the Firebase codelab for web. Whichever one you take, it will ensure you're much better prepared for interacting with the database through Cloud Functions.

As a final warning: you're nesting multiple data types under a single list. This is not recommended, since it leads to all kinds of problems down the line. Instead, I would pull the registered users into their own top-level node, so that you get:

{
  "events" : {
    "XXX" : {
      "eventHost" : "YYY",
      "eventID" : "XXX"
    }
  },
  "registered" : {
    "XXX" : {
      "ASKDJHAIUCHA" : {
        "name" : "Emma Watson",
        "userUID" : "ASKDJHAIUCHA" 
      }
    }
  },
  "users" : {
    "YYY" : {
      "deviceID" : "1234456",
      "name" : "Andrew Garfield",
      "userUID" : "YYY"
    }
  }
}

来源：https://stackoverflow.com/questions/42871379/firebase-cloudfunctions-querying-nodes