Annotating a Map with Custom Data

At a glance

Project structure

Source bundle/
├── MapCallouts/
│   ├── AppDelegate.swift
│   ├── CustomAnnotationView.swift
│   ├── DetailViewController.swift
│   ├── MapViewController.swift
│   ├── Annotations/
│   │   ├── BridgeAnnotation.swift
│   │   ├── CustomAnnotation.swift
│   │   ├── FerryBuildingAnnotation.swift
│   │   └── SanFranciscoAnnotation.swift
│   └── Resources/
│       └── Base.lproj/
│           └── LaunchScreen.storyboard
├── Configuration/
│   └── SampleCode.xcconfig
└── MapCallouts.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

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 8 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["DetailViewController"]
    N3["MapKit APIs"]
    N1 --> N2
    N2 --> N3

Reference code

MapCallouts/AppDelegate.swift:10 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
}

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 MapKit.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    CustomAnnotationView *-- CGFloat : boxInset
    CustomAnnotationView *-- CGFloat : interItemSpacing
    CustomAnnotationView *-- CGFloat : maxContentWidth

Ownership evidence

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

@UIApplicationMain
class AppDelegate: 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.

Class and protocol design

MapCallouts/AppDelegate.swift:11 — representative type boundary

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
}

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

Access control

Reference code

MapCallouts/CustomAnnotationView.swift:13 — representative boundary

    private let boxInset = CGFloat(10)
    private let interItemSpacing = CGFloat(10)
    private let maxContentWidth = CGFloat(90)
    private let contentInsets = UIEdgeInsets(top: 10, left: 30, bottom: 20, right: 20)
    
    private let blurEffect = UIBlurEffect(style: .systemThickMaterial)

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: Controller: DetailViewController, MapViewController; Delegate: AppDelegate; View: CustomAnnotationView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: prepareForReuse, prepareForDisplay, layoutSubviews, viewDidLoad, doneAction, registerMapAnnotationViews, centerMapOnSanFrancisco, displayOne.
• Files: MapCallouts/AppDelegate.swift, MapCallouts/CustomAnnotationView.swift, MapCallouts/DetailViewController.swift, MapCallouts/MapViewController.swift, MapCallouts/Annotations/BridgeAnnotation.swift, MapCallouts/Annotations/CustomAnnotation.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches MapKit, UIKit 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