Sample CodeiOS, iPadOS, Mac CatalystReviewed 2026-07-21View on Apple Developer

Creating turn-based games

At a glance

Item Summary
Purpose Develop games where multiple players take turns and can exchange data while waiting for their turn.
App architecture A Swift sample with the source-visible chain TurnBasedGameSampleAppContentViewGameKit APIs.
Main patterns Delegate or data-source callbacks, Publisher-backed observable state, Actor-isolated state
Project style 9 scanned source file(s) across Swift, organized around ranked entry, type, and file boundaries.

Project structure

Source bundle/
├── TurnBasedGameSample/
│   ├── TurnBasedGameSampleApp.swift
│   ├── GameView.swift
│   ├── ChatView.swift
│   ├── ContentView.swift
│   ├── MessageView.swift
│   ├── TurnBasedGame+GKTurnBasedMatchmakerViewControllerDelegate.swift
│   ├── TurnBasedGame+MatchData.swift
│   ├── TurnBasedGame.swift
│   └── TurnBasedGame+GKTurnBasedEventListener.swift
├── Configuration/
│   └── SampleCode.xcconfig
├── Turn-Based Game Sample.entitlements
└── Turn-Based Game Sample.xcodeproj/
    └── .xcodesamplecode.plist

Structure observations

  • Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
  • Primary languages: Swift.
  • The verified tree contains 4 project/configuration file(s) and 10 source declaration(s).

Overall architecture

Reference code

TurnBasedGameSample/TurnBasedGameSampleApp.swift:10 — architecture anchor

@main
struct TurnBasedGameSampleApp: App {
    
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into GameKit.

Ownership and state

Ownership evidence

TurnBasedGameSample/GameView.swift:12 — stored dependency or nearest verified ownership anchor

struct GameView: View {
    // ...
    @ObservedObject var game: TurnBasedGame
    // ...
}
Owner Object or state Relationship Mutation authority
GameView TurnBasedGame (game) observes externally owned state The observed object is authoritative
GameView Bool (showMessages) owns wrapper-managed state Owning lexical scope
ChatView TurnBasedGame (game) observes externally owned state The observed object is authoritative
ChatView String (typingMessage) owns wrapper-managed state Owning lexical scope

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Class and protocol design

TurnBasedGameSample/TurnBasedGameSampleApp.swift:11 — representative type boundary

struct TurnBasedGameSampleApp: App {
    // ...
}
Type Responsibility Depends on or conforms to
TurnBasedGameSampleApp Application entry and top-level composition App
GameView User-interface presentation and input forwarding View
ChatView User-interface presentation and input forwarding View
ContentView User-interface presentation and input forwarding View
MessageView User-interface presentation and input forwarding View
MessageButtonStyle Represents a feature value or composable behavior ButtonStyle
Message Represents a feature value or composable behavior Identifiable
Participant Represents a feature value or composable behavior Identifiable
GameData Represents feature data Codable
TurnBasedGame Owns feature behavior and collaborator lifecycle NSObject, GKMatchDelegate, GKLocalPlayerListener, ObservableObject

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Symbol Access Verified effect Likely rationale
typingMessage (TurnBasedGameSample/ChatView.swift:13) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: keep state mutation or dependency lifetime inside the owning implementation.
game (TurnBasedGameSample/ContentView.swift:11) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: keep state mutation or dependency lifetime inside the owning implementation.
showMessages (TurnBasedGameSample/GameView.swift:13) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: keep state mutation or dependency lifetime inside the owning implementation.

Reference code

TurnBasedGameSample/ChatView.swift:13 — representative boundary

struct ChatView: View {
    // ...
    @State private var typingMessage: String = ""
    
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Logic Owning type or file Placement rationale
Application entry and top-level composition TurnBasedGameSampleApp The source’s App suffix makes this role explicit.
User-interface presentation and input forwarding ChatView, ContentView, GameView, MessageView The source’s View suffix makes this role explicit.

Design patterns

Pattern Source evidence Purpose or tradeoff
Delegate or data-source callbacks TurnBasedGameSample/TurnBasedGame.swift:13 Callback protocols invert event delivery back into the sample’s owner.
Publisher-backed observable state TurnBasedGameSample/TurnBasedGame.swift:24 Published properties notify observers while mutation remains with the state object.
Actor-isolated state TurnBasedGameSample/TurnBasedGame.swift:12 Actor annotations make the concurrency ownership boundary explicit.

Naming conventions

  • Types: App: TurnBasedGameSampleApp; View: ChatView, ContentView, GameView, MessageView.
  • Protocols: no local protocol declaration in the scanned source.
  • Methods: makeBody, turnBasedMatchmakerViewControllerWasCancelled, turnBasedMatchmakerViewController, encodeGameData, encode, decodeGameData, resetGame, authenticatePlayer.
  • Files: TurnBasedGameSample/TurnBasedGameSampleApp.swift, TurnBasedGameSample/GameView.swift, TurnBasedGameSample/ChatView.swift, TurnBasedGameSample/ContentView.swift, TurnBasedGameSample/MessageView.swift, TurnBasedGameSample/TurnBasedGame.swift.

Architecture takeaways

  • TurnBasedGameSampleApp is the main source-visible entry or composition anchor for this sample.
  • Framework work reaches SwiftUI, GameKit through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
  • Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
  • Access-control conclusions separate verified language visibility from the likely design rationale.
  • The source does not justify labeling the design protocol-oriented.

Source map

Source file Relevant symbols
TurnBasedGameSample/TurnBasedGameSampleApp.swift TurnBasedGameSampleApp
TurnBasedGameSample/GameView.swift GameView, GameViewPreviews, MessageButtonStyle
TurnBasedGameSample/ChatView.swift ChatView, ChatViewPreviews
TurnBasedGameSample/ContentView.swift ContentView, ContentViewPreviews
TurnBasedGameSample/MessageView.swift MessageView, MessageViewPreviews
TurnBasedGameSample/TurnBasedGame+GKTurnBasedMatchmakerViewControllerDelegate.swift Feature implementation
TurnBasedGameSample/TurnBasedGame+MatchData.swift Message, Participant, GameData
TurnBasedGameSample/TurnBasedGame.swift TurnBasedGame
TurnBasedGameSample/TurnBasedGame+GKTurnBasedEventListener.swift Feature implementation