Send and receive data from GameCenter: Swift

Question

I'm creating a game that uses GameCenter and I'm trying to send and retrieve data.

This is how I'm sending data: (the function 'sendData' is provided by GameCenter with GameKit)

let nick = GCHelper()
let data = NSData(contentsOfFile: "")
try! nick.match.sendData(toAllPlayers: data as! Data, with: .reliable)

'GCHelper' is a class I'm using that contains many functions for Game Center, a download is further through the questions if you're interested. I just needed to call it to access the function.

Then to retrieve data I'm attempting to use this:

nick.match(GKMatch, didReceive: Data, fromPlayer: String)

Note: I have not filled in any of the above parameters

Here is the function I'm using to retrieve the data:

public func match(_ theMatch: GKMatch, didReceive data: Data, fromPlayer playerID: String) {
    if match != theMatch {
        return
    }

    delegate?.match(theMatch, didReceiveData: data, fromPlayer: playerID)
}

The function I'm using 'match()' is apart of the GCHelper class. GCHelper allows for you to create GameCenter game easier. Here is a link in case you want to reference it: https://github.com/jackcook/GCHelper

QUESTION Now that I've showed you all the methods, how would I use the previous method to retrieve data? One of its parameters is 'fromPlayer' and asks for the playerId(String), but how would I know what the other players playerID is? Better yet, how would I retrieve it?

If you don't think this is a good way to handle retrieving data, how could I do it better? Is there another way to do this?

Key Facts: The game requires 2 people and data is being exchanged between these 2 people only. I need to know how to send and retrieve data amongst the 2. Thanks for the help! If you have any questions let me know.

Answer 1

This is the function I'm using to retrieve the data:

open func match(_ theMatch: GKMatch, didReceive data: Data, fromPlayer playerID: String) {
}

Now, the data I'm sending is a string. So I create a variable that unarchives the data and sets it to string format.

let myString = NSKeyedUnarchiver.unarchiveObject(with: data) as! String

After this, I need a way to get that string from the view controller or game center file to my game scene. In which I simply just stored the data using UserDefaults.

let user = UserDefaults.standard
user.set(myString, forKey: "myString")

Then in my SKScene I created a timer, in which it checks every couple of seconds to see if there's a change. It stores the values so that when a new values arrives it can compare and if it is different it does something with it, for example: update player points.

Note: This is what I found to work, someone else may have a better way, but it works fine for me.