Creating a MIDI device driver

At a glance

Project structure

Source bundle/
├── CreatingMIDIDriverSampleApp/
│   ├── CreatingMIDIDriverSampleApp.swift
│   ├── CreatingMIDIDriverSampleAppViewModel.swift
│   ├── CreatingMIDIDriverSampleAppUserClient.mm
│   ├── CreatingMIDIDriverSampleAppView.swift
│   ├── CreatingMIDIDriverSampleAppUserClient.h
│   ├── CreatingMIDIDriverSampleAppDriverKeys.h
│   └── CreatingMIDIDriverSampleApp.entitlements
├── CreatingMIDIDriverSampleAppExtension/
│   ├── CreatingMIDIDriverSampleAppDriverUserClient.cpp
│   ├── CreatingMIDIDriverSampleAppDevice.cpp
│   ├── CreatingMIDIDriverSampleAppDriver.cpp
│   └── CreatingMIDIDriverSampleAppDriverKeys.h
└── Configuration/
    └── SampleCode.xcconfig

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C++, C/Objective-C header, Objective-C++, Swift.
• The verified tree contains 7 project/configuration file(s) and 10 source declaration(s).

Overall architecture

flowchart LR
    N1["CreatingMIDIDriverSampleApp"]
    N2["CreatingMIDIDriverSampleAppView"]
    N3["CreatingMIDIDriverSampleAppViewModel"]
    N4["CreatingMIDIDriverSampleAppUserClient"]
    N5["DriverKit / MIDIDriverKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleApp.swift:10 — architecture anchor

@main
struct CreatingMIDIDriverSampleApp: App {
    var body: some Scene {
        WindowGroup {
            CreatingMIDIDriverSampleAppView()
        }
    }
}

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 MIDIDriverKit.

Ownership and state

classDiagram
    CreatingMIDIDriverSampleAppViewModel o-- State : state
    CreatingMIDIDriverSampleAppViewModel *-- String : dextIdentifier
    CreatingMIDIDriverSampleAppUserClient o-- io_object_t : ioObject
    CreatingMIDIDriverSampleAppUserClient o-- io_connect_t : ioConnection

Ownership evidence

CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleAppViewModel.swift:94 — stored dependency or nearest verified ownership anchor

class CreatingMIDIDriverSampleAppViewModel: NSObject {
    // ...
    @Published private var state: CreatingMIDIDriverSampleAppStateMachine.State = .unloaded
    // ...
}

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

CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleApp.swift:11 — representative type boundary

struct CreatingMIDIDriverSampleApp: App {
    var body: some Scene {
        WindowGroup {
            CreatingMIDIDriverSampleAppView()
        }
    }
}

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

Access control

Reference code

CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleAppUserClient.mm:13 — representative boundary

@interface CreatingMIDIDriverSampleAppUserClient()
@property io_object_t ioObject;
@property io_connect_t ioConnection;
@end

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: App: CreatingMIDIDriverSampleApp; Client: CreatingMIDIDriverSampleAppUserClient; View: CreatingMIDIDriverSampleAppView; ViewModel: CreatingMIDIDriverSampleAppViewModel.
• Protocols: no local protocol declaration in the scanned source.
• Methods: onUnloaded, onActivatingOrNeedsApproval, onActivated, onActivationError, process, activateMyDext, activateExtension, deactivateExtension.
• Files: CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleApp.swift, CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleAppViewModel.swift, CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleAppUserClient.mm, CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleAppView.swift, CreatingMIDIDriverSampleApp/CreatingMIDIDriverSampleAppUserClient.h.

Architecture takeaways

• CreatingMIDIDriverSampleApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches DriverKit, MIDIDriverKit, SwiftUI, IOKit 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

• Official Apple documentation