TicTacFish: Implementing a game using distributed actors

At a glance

Project structure

Source bundle/
├── Step 2 Distributed Remote Bot/
│   ├── Server/
│   │   └── Sources/
│   │       └── TicTacFishServer/
│   │           └── boot.swift
│   ├── App/
│   │   └── TicTacFish/
│   │       └── TicTacFish/
│   │           └── TicTacFishApp.swift
│   └── Shared/
│       └── Sources/
│           └── TicTacFishShared/
│               ├── ActorSystems/
│               │   └── WebSocket/
│               │       └── WebSocketActorSystem.swift
│               └── ViewModel/
│                   └── GameViewModel.swift
├── Step 0 Offline Local Only/
│   └── App/
│       └── TicTacFish/
│           └── TicTacFish/
│               ├── TicTacFishApp.swift
│               └── GameView.swift
├── Step 1 Distributed yet still Local Bot/
│   └── App/
│       └── TicTacFish/
│           └── TicTacFish/
│               └── TicTacFishApp.swift
├── Step 3 Distributed Local Network Player/
│   └── App/
│       └── TicTacFish/
│           └── TicTacFish/
│               └── TicTacFishApp.swift
└── Configuration/
    └── SampleCode.xcconfig

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 26 project/configuration file(s) and 111 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["Step 0 Offline Local Only"]
    V2["Step 1 Distributed yet still Local Bot"]
    V3["Step 2 Distributed Remote Bot"]
    V4["Step 3 Distributed Local Network Player"]
    Boundary["Distributed APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary
    Bundle --> V3
    V3 --> Boundary
    Bundle --> V4
    V4 --> Boundary

Reference code

Step 2 Distributed Remote Bot/Server/Sources/TicTacFishServer/boot.swift:17 — architecture anchor

@main
struct Boot {

    static func main() {
        let system = try! WebSocketActorSystem(mode: .serverOnly(host: "localhost", port: 8888))

        system.registerOnDemandResolveHandler { id in
            // We create new BotPlayers "ad-hoc" as they are requested for.
            // Subsequent resolves are able to resolve the same instance.
            if system.isBotID(id) {
                return system.makeActorWithID(id) {
                    OnlineBotPlayer(team: .rodents, actorSystem: system)
                }
            }

            return nil // don't resolve on-demand
        }

        print("========================================================")
        print("=== TicTacFish Server Running on: ws://\(system.host):\(system.port) ==")
        print("========================================================")

        Thread.sleep(forTimeInterval: 100_000)
        print("Done.")
    }
}

Interpretation

The branches represent separate entry-bearing project variants in the downloaded bundle, not runtime calls between those variants. Each branch is intentionally collapsed at the documented framework boundary; the detailed target-local flow remains in the cited files. Ownership is claimed only where the next section cites a stored property or assignment.

Ownership and state

classDiagram
    GameView *-- GameViewModel : model
    GameView o-- GameMode : mode
    GameView o-- OfflinePlayer : player
    GameView o-- Model : _model

Ownership evidence

Step 0 Offline Local Only/App/TicTacFish/TicTacFish/GameView.swift:13 — stored dependency or nearest verified ownership anchor

struct GameView: View {
    // ...
    @StateObject private var model: GameViewModel
    // ...
}

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.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

Step 0 Offline Local Only/App/TicTacFish/TicTacFish/GameFieldView.swift:16 — representative execution boundary

struct GameFieldView: View {
    // ...
    let action: (Int) async throws -> Void
    // ...
}

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

Step 1 Distributed yet still Local Bot/Shared/Sources/TicTacFishShared/Game/Players.swift:42 — representative type boundary

public protocol GamePlayer: AnyActor, Identifiable where ID == ActorIdentity {
    // ...
    func makeMove() async throws -> GameMove
    // ...
}

The source explicitly defines local protocol relationships: RandomPlayerBotAI → PlayerBotAI, RandomPlayerBotAI → PlayerBotAI, OfflinePlayer → GamePlayer, RandomPlayerBotAI → PlayerBotAI, OfflinePlayer → GamePlayer, OnlineBotPlayer → GamePlayer.

Access control

Reference code

Step 0 Offline Local Only/App/TicTacFish/TicTacFish/GameFieldView.swift:13 — representative boundary

struct GameFieldView: View {
    // ...
    @StateObject private var model: GameViewModel
    // ...
}

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

Design patterns

Main application flow

sequenceDiagram
    participant WebSocketActorSystem
    participant Task
    participant _openExistential
    participant handler
    WebSocketActorSystem->>Task: Start asynchronous work
    WebSocketActorSystem->>WebSocketActorSystem: executeDistributedTarget()
    WebSocketActorSystem->>_openExistential: _openExistential()
    WebSocketActorSystem->>handler: onThrow()

Reference code

Step 2 Distributed Remote Bot/Shared/Sources/TicTacFishShared/ActorSystems/WebSocket/WebSocketActorSystem.swift:373 — receiveInboundCall()

    func receiveInboundCall(envelope: RemoteWebSocketCallEnvelope, on channel: Channel) {
        // ...
        log("receive-inbound", "Envelope: \(envelope)")
        Task {
            log("receive-inbound", "Resolve any: \(envelope.recipient)")
            guard let anyRecipient = resolveAny(id: envelope.recipient, resolveReceptionist: true) else {
                log("deadLetter", "[warn] \(#function) failed to resolve \(envelope.recipient)")
                return
            }
            log("receive-inbound", "Recipient: \(anyRecipient)")
            let target = RemoteCallTarget(envelope.invocationTarget)
            log("receive-inbound", "Target: \(target)")
            log("receive-inbound", "Target.identifier: \(target.identifier)")
            let handler = ResultHandler(actorSystem: self, callID: envelope.callID, system: self, channel: channel)
            log("receive-inbound", "Handler: \(anyRecipient)")
            do {
                var decoder = Self.InvocationDecoder(system: self, envelope: envelope)
                func doExecuteDistributedTarget<Act: DistributedActor>(recipient: Act) async throws {
                    log("receive-inbound", "executeDistributedTarget")
                    try await executeDistributedTarget(
                        on: recipient,
                        target: target,
                        invocationDecoder: &decoder,
                        handler: handler)
                }
                try await _openExistential(anyRecipient, do: doExecuteDistributedTarget)
            } catch {
                log("inbound", "[error] failed to executeDistributedTarget [\(target)] on [\(anyRecipient)], error: \(error)")
                try! await handler.onThrow(error: error)
            }
        }
    }

Naming conventions

• Types: App: TicTacFishApp; Handler: BonjourResultHandler, HTTPHandler, HTTPInitialRequestHandler, WebSocketActorMessageInboundHandler, WebSocketActorSystemResultHandler; Player: BotPlayer, GamePlayer, LocalNetworkPlayer, OfflinePlayer, OnlineBotPlayer; System: WebSocketActorSystem; View: GameFieldView, GameView, MainMenuView, TitleView; ViewModel: GameViewModel.
• Protocols: GamePlayer, GamePlayer, GamePlayer, PlayerBotAI, PlayerBotAI, PlayerBotAI, PlayerBotAI, DistributedActorReceptionist.
• Methods: main, syncShutdownGracefully, assignID, actorReady, resignID, resolve, resolveAny, makeInvocationEncoder.
• Files: Step 0 Offline Local Only/App/TicTacFish/TicTacFish/TicTacFishApp.swift, Step 1 Distributed yet still Local Bot/App/TicTacFish/TicTacFish/TicTacFishApp.swift, Step 2 Distributed Remote Bot/App/TicTacFish/TicTacFish/TicTacFishApp.swift, Step 3 Distributed Local Network Player/App/TicTacFish/TicTacFish/TicTacFishApp.swift, Step 2 Distributed Remote Bot/Shared/Sources/TicTacFishShared/ActorSystems/WebSocket/WebSocketActorSystem.swift, Step 0 Offline Local Only/App/TicTacFish/TicTacFish/GameView.swift.

Architecture takeaways

• boot is the main source-visible entry or composition anchor for this sample.
• Framework work reaches Distributed, SwiftUI, TicTacFishShared, NIOCore 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.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation