Becoming a now playable app

At a glance

Project structure

Source bundle/
├── NowPlayable-Mac/
│   └── Interface/
│       ├── MacAppDelegate.swift
│       ├── MacCommandCellView.swift
│       ├── MacConfigViewController.swift
│       ├── MacEnabledItemCellView.swift
│       └── MacWindowController.swift
├── NowPlayable-iOS/
│   └── Interface/
│       ├── IOSAppDelegate.swift
│       ├── IOSConfigTableViewController.swift
│       └── IOSConfigViewController.swift
├── NowPlayable-tvOS/
│   └── Interface/
│       ├── TVAppDelegate.swift
│       └── TVConfigViewController.swift
└── Shared/
    ├── Player/
    │   └── AssetPlayer.swift
    └── Configuration/
        └── ConfigCommand.swift

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 12 project/configuration file(s) and 32 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["NowPlayable-Mac"]
    V2["NowPlayable-iOS"]
    V3["NowPlayable-tvOS"]
    Boundary["MediaPlayer APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary
    Bundle --> V3
    V3 --> Boundary

Reference code

NowPlayable-Mac/Interface/MacAppDelegate.swift:10 — architecture anchor

@NSApplicationMain
class MacAppDelegate: NSObject, NSApplicationDelegate {

    // A direct reference to this app delegate.

    static private(set) var shared: MacAppDelegate!

    // Initial setup when the app has finished launching.

    func applicationDidFinishLaunching(_ notification: Notification) {

        MacAppDelegate.shared = self

        // Create the data model.

        ConfigModel.shared = ConfigModel(nowPlayableBehavior: MacNowPlayableBehavior())

        // Notify the UI that the model has been changed.

        MacWindowController.shared.updateConfig()
    }

}

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
    IOSAppDelegate o-- UIWindow : window
    TVAppDelegate o-- UIWindow : window
    MacCommandCellView o-- NSTextField : commandNameLabel
    MacCommandCellView o-- NSButton : disabledButton

Ownership evidence

NowPlayable-iOS/Interface/IOSAppDelegate.swift:20 — stored dependency or nearest verified ownership anchor

@UIApplicationMain
class IOSAppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

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.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@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.

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

Shared/Utility/CommandCellViewDelegate.swift:10 — representative type boundary

protocol CommandCellViewDelegate: AnyObject {
    // ...
    func updateCommandDisabledState(_ configPath: ConfigPath, disabled: Bool)
    // ...
}

The source explicitly defines local protocol relationships: MacNowPlayableBehavior → NowPlayable, IOSConfigTableViewController → CommandCellViewDelegate, IOSConfigTableViewController → EnabledItemCellViewDelegate, IOSNowPlayableBehavior → NowPlayable, TVNowPlayableBehavior → NowPlayable.

Access control

Reference code

NowPlayable-Mac/Interface/MacConfigViewController.swift:122 — representative boundary

    private func cellForExternalPlayback(_ tableView: NSTableView, row: Int, item itemIndex: Int) -> NSTableCellView? {
        // ...
        guard let cell = tableView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "EnabledItemCell"),
                                            owner: self) as? MacEnabledItemCellView
        // ...
    }

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

Naming conventions

• Types: Command: ConfigCommand, NowPlayableCommand; Controller: IOSConfigTableViewController, IOSConfigViewController, MacConfigViewController, MacWindowController, TVConfigViewController; Delegate: CommandCellViewDelegate, EnabledItemCellViewDelegate, IOSAppDelegate, MacAppDelegate, TVAppDelegate; Model: ConfigModel; Player: AssetPlayer; View: AssetPlayerView, MacCommandCellView, MacEnabledItemCellView.
• Protocols: CommandCellViewDelegate, EnabledItemCellViewDelegate, NowPlayable.
• Methods: applicationDidFinishLaunching, application, optOut, handlePlayerItemChange, handlePlaybackChange, play, pause, togglePlayPause.
• Files: NowPlayable-Mac/Interface/MacAppDelegate.swift, NowPlayable-iOS/Interface/IOSAppDelegate.swift, NowPlayable-tvOS/Interface/TVAppDelegate.swift, Shared/Player/AssetPlayer.swift, NowPlayable-Mac/Interface/MacCommandCellView.swift, NowPlayable-Mac/Interface/MacConfigViewController.swift.

Architecture takeaways

• MacAppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, AVFoundation, MediaPlayer, Cocoa 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