GameKitUI.swift

GameKit (GameCenter) helper for SwiftUI

GameKitUI is created and maintaned with ❥ by Sascha Muellner.

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What?

This is a Swift package with support for iOS that allows to use GameKit with SwiftUI.

Requirements

The latest version of GameKitUI requires:

• Swift 5+
• iOS 13+
• Xcode 11+

Installation

Swift Package Manager

Using SPM add the following to your dependencies

'GameKitUI', 'main', 'https://github.com/SwiftPackageRepository/GameKitUI.swift.git'

How to use?

Views

GameCenter Authentication

To authenticate the player with GameCenter just show the authentication view GKAuthenticationView.

import SwiftUI
import GameKitUI

struct ContentView: View {
	var body: some View {
		GKAuthenticationView { (state) in
			switch state {
			    case .started:
			    	print("Authentication Started")
			    	break
			    case .failed:
			    	print("Failed")
			    	break
			    case .deauthenticated:
					print("Deauthenticated")
			      	break
			    case .succeeded:
			    	break
			}
		} failed: { (error) in
			print("Failed: \(error.localizedDescription)")
		} authenticated: { (playerName) in
			print("Hello \(playerName)")
		}
	}
}

GameKit Invite

Invites created by a GameKit MatchMaker or TurnBasedMatchmaker can be handled using a GKMatchMakerView.

import SwiftUI
import GameKitUI

struct ContentView: View {
    var body: some View {
        GKInviteView(
            invite: GKInvite()
        ) {
        } failed: { (error) in
            print("Invitation Failed: \(error.localizedDescription)")
        } started: { (match) in
            print("Match Started")
        }
    }
}

GameKit MatchMaker

Match making for a live match can be initiated via the GKMatchMakerView.

import SwiftUI
import GameKitUI

struct ContentView: View {
	var body: some View {
		GKMatchMakerView(
                    minPlayers: 2,
                    maxPlayers: 4,
                    inviteMessage: "Let us play together!"
                ) {
                    print("Player Canceled")
                } failed: { (error) in
                    print("Match Making Failed: \(error.localizedDescription)")
                } started: { (match) in
                    print("Match Started")
                }
	}
}

GameKit TurnBasedMatchmaker

To start a turn based match use GKTurnBasedMatchmakerView.

import SwiftUI
import GameKitUI

struct ContentView: View {
	var body: some View {
		GKTurnBasedMatchmakerView(
                    minPlayers: 2,
                    maxPlayers: 4,
                    inviteMessage: "Let us play together!"
                ) {
                    print("Player Canceled")
                } failed: { (error) in
                    print("Match Making Failed: \(error.localizedDescription)")
                } started: { (match) in
                    print("Match Started")
                }
	}
}

GameKit Manager

GKMatchManager

GameKitUI views rely on a manager singelton GKMatchManager, which listens to GameKit state changes of the match making process. Changes to the local player GKLocalPlayer, invites GKInvite or matches GKMatch can be observed using the provided public subjects CurrentValueSubject.

import SwiftUI
import GameKitUI

class ViewModel: ObservableObject {

    @Published public var gkInvite: GKInvite?
    @Published public var gkMatch: GKMatch?

    private var cancellableInvite: AnyCancellable?
    private var cancellableMatch: AnyCancellable?
    private var cancellableLocalPlayer: AnyCancellable?

    public init() {
        self.cancellableInvite = GKMatchManager
            .shared
            .invite
            .sink { (invite) in
                self.gkInvite = invite.gkInvite
        }
        self.cancellableMatch = GKMatchManager
            .shared
            .match
            .sink { (match) in
                self.gkMatch = match.gkMatch
        }
        self.cancellableLocalPlayer = GKMatchManager
            .shared
            .localPlayer
            .sink { (localPlayer) in
                // current GKLocalPlayer.local
        }
    }
    
    deinit() {
        self.cancellableInvite?.cancel()
        self.cancellableMatch?.cancel()
        self.cancellableLocalPlayer?.cancel()
    }
}

Examples

GKMatchMaker Example

The provided GKMatchMaker example, includes a full working SwiftUI solution for handling GameKit matchmaking. Just copy the file Config.xcconfig-example to Config.xcconfig and add your development team ID for the variable XCCONFIG_DEVELOPMENT_TEAM and a valid Bundle ID with GameCenter support for XCCONFIG_BUNDLE_ID. The Config.xcconfig should now look something like this:

// Configuration settings file format documentation can be found at:
// https://help.apple.com/xcode/#/dev745c5c974

XCCONFIG_DEVELOPMENT_TEAM = 9988XX7D42 // YOUR DEVELOPMENT TEAM ID
XCCONFIG_BUNDLE_ID = com.yourcompany.ProductName // A BUNDLE ID WITH SUPPORT FOR THE GAMECENTER CAPABILITY

Then open the GKMatchMaker.xcodeproj and run it on as many real hardware devices to test the GameKit match making.

Documentation

• Apple Documentation GameKit
• raywenderlich.com: Game Center for iOS: Building a Turn-Based Game
• raywenderlich.com: Game Center Tutorial: How To Make A Simple Multiplayer Game with Sprite Kit: Part 1/2
• Medium: GameKit Real Time Multiplayer Tutorial