Sample CodeiOS, iPadOSReviewed 2026-07-21View on Apple Developer

Recognizing and Labeling Arbitrary Objects

At a glance

Item Summary
Purpose Create anchors that track objects you recognize in the camera feed, using a custom optical-recognition algorithm.
App architecture A Swift sample with the source-visible chain AppDelegateStatusViewControllerARKit APIs.
Main patterns View-controller organization, Delegate or data-source callbacks
Project style 5 scanned source file(s) across Swift, organized around ranked entry, type, and file boundaries.

Project structure

Source bundle/
├── ARKitVision/
│   ├── Support/
│   │   ├── AppDelegate.swift
│   │   ├── StatusViewController.swift
│   │   └── Utilities.swift
│   ├── ViewController.swift
│   ├── TemplateLabelNode.swift
│   └── Resources/
│       ├── Base.lproj/
│       │   └── LaunchScreen.storyboard
│       ├── Info.plist
│       └── Main.storyboard
├── ARKitVision.xcodeproj/
│   ├── .xcodesamplecode.plist
│   └── project.pbxproj
└── 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 6 project/configuration file(s) and 5 source declaration(s).

Overall architecture

Reference code

ARKitVision/Support/AppDelegate.swift:11 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
}

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 ARKit.

Ownership and state

Ownership evidence

ARKitVision/Support/AppDelegate.swift:13 — stored dependency or nearest verified ownership anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    // ...
}
Owner Object or state Relationship Mutation authority
AppDelegate UIWindow (window) stores or receives App/module collaborators
StatusViewController Array (all) owns value state App/module collaborators
StatusViewController Callback (restartExperienceHandler) stores a callback App/module collaborators
StatusViewController TimeInterval (displayDuration) stores or receives Initialized by the owner; the binding is immutable

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

ARKitVision/Support/AppDelegate.swift:12 — representative type boundary

class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
}
Type Responsibility Depends on or conforms to
AppDelegate Receives callback-driven events UIResponder, UIApplicationDelegate
StatusViewController View lifecycle, callbacks, and feature coordination UIViewController
ViewController View lifecycle, callbacks, and feature coordination UIViewController, UIGestureRecognizerDelegate, ARSKViewDelegate, ARSessionDelegate
MessageType Defines a closed set of feature states or choices Concrete collaborators/imported frameworks
TemplateLabelNode Owns feature behavior and collaborator lifecycle SKReferenceNode

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
displayDuration (ARKitVision/Support/StatusViewController.swift:47) 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.
messageHideTimer (ARKitVision/Support/StatusViewController.swift:50) 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.
timers (ARKitVision/Support/StatusViewController.swift:52) 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.
restartExperience (ARKitVision/Support/StatusViewController.swift:119) private Use is restricted to the lexical declaration and same-file extensions allowed by Swift. Inference: hide an implementation step that is not part of the collaboration surface.

Reference code

ARKitVision/Support/StatusViewController.swift:47 — representative boundary

    private let displayDuration: TimeInterval = 6
    
    // Timer for hiding messages.
    private var messageHideTimer: Timer?
    
    private var timers: [MessageType: Timer] = [:]

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
View lifecycle, callbacks, and feature coordination StatusViewController, ViewController The source’s Controller suffix makes this role explicit.
Receives callback-driven events AppDelegate The source’s Delegate suffix makes this role explicit.

Design patterns

Pattern Source evidence Purpose or tradeoff
View-controller organization ARKitVision/Support/StatusViewController.swift:16 A controller is the verified coordination boundary; this is MVC-style only where a separate model is present.
Delegate or data-source callbacks ARKitVision/Support/AppDelegate.swift:12 Callback protocols invert event delivery back into the sample’s owner.

Naming conventions

  • Types: Controller: StatusViewController, ViewController; Delegate: AppDelegate.
  • Protocols: no local protocol declaration in the scanned source.
  • Methods: application, showMessage, scheduleMessage, cancelScheduledMessage, cancelAllScheduledMessages, showTrackingQualityInfo, escalateFeedback, restartExperience.
  • Files: ARKitVision/Support/AppDelegate.swift, ARKitVision/Support/StatusViewController.swift, ARKitVision/ViewController.swift, ARKitVision/TemplateLabelNode.swift.

Architecture takeaways

  • AppDelegate is the main source-visible entry or composition anchor for this sample.
  • Framework work reaches ARKit, SpriteKit, UIKit, Vision 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
ARKitVision/Support/AppDelegate.swift AppDelegate
ARKitVision/Support/StatusViewController.swift StatusViewController, MessageType
ARKitVision/ViewController.swift ViewController
ARKitVision/TemplateLabelNode.swift TemplateLabelNode
ARKitVision/Support/Utilities.swift Feature implementation