Monitoring location changes with Core Location

At a glance

Project structure

Source bundle/
├── LocationMonitorSampleApp/
│   ├── LocationMonitorSampleApp.swift
│   ├── ContentView.swift
│   ├── AppDelegate.swift
│   └── Info.plist
├── Configuration/
│   └── SampleCode.xcconfig
└── LocationMonitorSampleApp.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 4 project/configuration file(s) and 5 source declaration(s).

Overall architecture

flowchart LR
    N1["LocationMonitorSampleApp"]
    N2["ContentView"]
    N3["ObservableMonitorModel"]
    N4["CoreLocation APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

LocationMonitorSampleApp/LocationMonitorSampleApp.swift:10 — architecture anchor

@main
struct LocationMonitorSampleApp: App {
    // ...
}

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 Core Location.

Ownership and state

classDiagram
    ContentView *-- CLLocationCoordinate2D : appleParkLocation
    ContentView *-- UUID : testBeaconId
    ObservableMonitorModel *-- ObservableMonitorModel : shared
    ObservableMonitorModel o-- CLMonitor : monitor

Ownership evidence

LocationMonitorSampleApp/ContentView.swift:12 — stored dependency or nearest verified ownership anchor

let appleParkLocation = CLLocationCoordinate2D(latitude: 37.3346, longitude: -122.0090)
let testBeaconId = UUID(uuidString: "A2C56DB5-DFFB-48D2-B060-D0F5A71096E0")!

let globalAuthDeniedError = "Please enable Location Services by going to Settings -> Privacy & Security"
let authDeniedError = "Please authorize LocationMonitorSampleApp to access Location Services"
let authRestrictedError = "LocationMonitorSampleApp can't access your location. Do you have Parental Controls enabled?"
let accuracyLimitedError = "LocationMonitorSampleApp can't function without access to your precise location"

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

LocationMonitorSampleApp/LocationMonitorSampleApp.swift:11 — representative type boundary

struct LocationMonitorSampleApp: App {
    // ...
}

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

Access control

Reference code

LocationMonitorSampleApp/ContentView.swift:38 — representative boundary

@MainActor
public class ObservableMonitorModel: ObservableObject {
    // ...
    public var monitor: CLMonitor?
    // ...
}

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

One launch starts a long-lived monitor task that registers conditions, restores their last events, and then reduces each asynchronous event into observable UI rows.

sequenceDiagram
    participant System as UIApplication
    participant App as AppDelegate
    participant Model as ObservableMonitorModel
    participant Monitor as CLMonitor
    participant UI as ContentView
    System-->>App: didFinishLaunching
    App->>Model: startMonitoringConditions()
    Model->>Monitor: Create named monitor
    Model->>Monitor: Add geographic and beacon conditions
    loop existing identifiers
        Model->>Monitor: record(for: identifier)
        Monitor-->>Model: lastEvent
    end
    loop asynchronous condition events
        Monitor-->>Model: events sequence yields event
        Model->>Monitor: read prior lastEvent
        Model-->>UI: Update published UIRows
    end

Reference code

LocationMonitorSampleApp/ContentView.swift:77 — the task registers both conditions before consuming the monitor’s event sequence.

func startMonitoringConditions() {
    Task {
        monitor = await CLMonitor(monitorName)

        await monitor!.add(getCircularGeographicCondition(), identifier: "ApplePark")
        await monitor!.add(getBeaconIdentityCondition(), identifier: "TestBeacon")
        for identifier in await monitor!.identifiers {
            guard let lastEvent = await monitor!.record(for: identifier)?.lastEvent else { continue }
            UIRows[identifier] = [lastEvent]
        }
        for try await event in await monitor!.events {
            guard let lastEvent = await monitor!.record(for: event.identifier)?.lastEvent else { continue }
            if event.state == lastEvent.state { continue }
            UIRows[event.identifier] = [event]
            UIRows[event.identifier]?.append(lastEvent)
        }
    }
}

Naming conventions

• Types: App: LocationMonitorSampleApp; Delegate: AppDelegate; Model: ObservableMonitorModel; View: ContentView, ErrorView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: without, startAuthSession, startMonitoringConditions, updateRecords, getCircularGeographicCondition, getBeaconIdentityCondition, application.
• Files: LocationMonitorSampleApp/LocationMonitorSampleApp.swift, LocationMonitorSampleApp/ContentView.swift, LocationMonitorSampleApp/AppDelegate.swift.

Architecture takeaways

• LocationMonitorSampleApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, CoreLocation, 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