Sample CodeiOS, iPadOS, Mac CatalystReviewed 2026-07-21View on Apple Developer

Managing location-based reminders

At a glance

Item Summary
Purpose Access reminders set up with geofence-enabled alarms on a person’s calendars.
App architecture A Swift sample with the source-visible chain LocationBasedRemindersAppContentViewLocationManagerEventKit APIs.
Main patterns Delegate or data-source callbacks, Central store, Binding-based state propagation, Actor isolation
Project style 32 scanned source file(s) across Swift, organized around ranked entry, type, and file boundaries.
Execution model Source-visible boundaries: await suspension point, Task, Sendable or @Sendable, @MainActor, actor; none alone proves a background thread.
State/event model Source-visible mechanisms: SwiftUI state property wrapper, @Observable, NotificationCenter.
Key frameworks/packages SwiftUI, EventKit, MapKit, Foundation, OSLog; these are source dependencies, not architecture labels.

Project structure

Source bundle/
└── LocationBasedReminders/
    ├── LocationBasedRemindersApp.swift
    ├── ReminderStore.swift
    ├── ReminderStoreManager.swift
    ├── ContentView.swift
    ├── LocationManager.swift
    ├── MainView.swift
    ├── MapView.swift
    ├── SourceModel.swift
    ├── WelcomeView.swift
    ├── MapAnnotation.swift
    ├── AnnotationImage.swift
    └── AppSettingsLink.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 4 project/configuration file(s) and 33 source declaration(s).

Overall architecture

Reference code

LocationBasedReminders/LocationBasedRemindersApp.swift:10 — architecture anchor

@main
struct LocationBasedRemindersApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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 EventKit.

Ownership and state

Ownership evidence

LocationBasedReminders/ReminderStore.swift:29 — stored dependency or nearest verified ownership anchor

actor ReminderStore {
    let eventStore: EKEventStore
    // ...
}
Owner Object or state Relationship Mutation authority
ReminderStore EKEventStore (eventStore) stores or receives Initialized by the owner; the binding is immutable
ReminderStoreManager ReminderStore (dataStore) stores or receives Initialized by the owner; the binding is immutable
ReminderStoreManager Logger (logger) creates and retains Initialized by the owner; the binding is immutable
ContentView ReminderStoreManager (manager) owns wrapper-managed state Owning lexical scope

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.

Concern Source mechanism Verified placement or handoff Evidence
Suspension boundary await suspension point The source declares or crosses an asynchronous boundary; it does not by itself establish background execution. LocationBasedReminders/ContentView.swift:16
Task creation Task The source creates an unstructured task; surrounding context determines inherited actor isolation. LocationBasedReminders/DeleteConfirmationButton.swift:24
Transfer contract Sendable or @Sendable The source declares a sendability boundary; this alone does not synchronize mutable state. LocationBasedReminders/Geofence.swift:11
Main isolation @MainActor The cited annotation marks its attached declaration or closure as main-actor isolated. LocationBasedReminders/LocationManager.swift:12
Actor isolation actor The cited type is actor-isolated; this does not select a background thread. LocationBasedReminders/ReminderStore.swift:28

@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.

Reference code

LocationBasedReminders/ContentView.swift:16 — representative execution boundary

struct ContentView: View {
    // ...
                await manager.listenForCalendarChanges()
    // ...
}

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.

Category Mechanism or module Verified role Evidence
State propagation SwiftUI state property wrapper A SwiftUI property wrapper supplies or observes UI state. LocationBasedReminders/AppSettingsLink.swift:12
State propagation @Observable Observation macro publishes source-visible changes. LocationBasedReminders/LocationManager.swift:13
State propagation NotificationCenter NotificationCenter distributes named process-local events. LocationBasedReminders/ReminderStoreManager.swift:52
Source import SwiftUI The cited file imports this module; runtime use and architectural role are not inferred. LocationBasedReminders/AnnotationImage.swift:8
Source import EventKit The cited file imports this module; runtime use and architectural role are not inferred. LocationBasedReminders/AppSettingsLink.swift:8
Source import MapKit The cited file imports this module; runtime use and architectural role are not inferred. LocationBasedReminders/EKReminder+Extension.swift:9
Source import Foundation The cited file imports this module; runtime use and architectural role are not inferred. LocationBasedReminders/Helpers.swift:8
Source import OSLog The cited file imports this module; runtime use and architectural role are not inferred. LocationBasedReminders/LocationManager.swift:8

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

LocationBasedReminders/LocationBasedRemindersApp.swift:11 — representative type boundary

@main
struct LocationBasedRemindersApp: App {
    // ...
            ContentView()
    // ...
}
Type Responsibility Depends on or conforms to
LocationBasedRemindersApp Application entry and top-level composition App
ReminderStore Centralized state or persistence access Concrete collaborators/imported frameworks
ReminderStoreManager Long-lived feature or framework coordination Concrete collaborators/imported frameworks
ContentView User-interface presentation and input forwarding View
LocationManager Long-lived feature or framework coordination NSObject
MainView User-interface presentation and input forwarding View
MapView User-interface presentation and input forwarding View
SourceModel Feature data or observable state Identifiable, Hashable, Sendable
WelcomeView User-interface presentation and input forwarding View
ReminderStoreError Represents feature failure conditions Error

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
openURL (LocationBasedReminders/AppSettingsLink.swift:12) 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.
manager (LocationBasedReminders/AppSettingsLink.swift:13) 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.
navigatetoSettings (LocationBasedReminders/AppSettingsLink.swift:26) 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.
navigateButton (LocationBasedReminders/AppSettingsLink.swift:33) 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.

Reference code

LocationBasedReminders/AppSettingsLink.swift:12 — representative boundary

struct AppSettingsLink: View {
    @Environment(\.openURL) private var openURL
    // ...
}

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
Application entry and top-level composition LocationBasedRemindersApp The source’s App suffix makes this role explicit.
Long-lived feature or framework coordination LocationManager, ReminderStoreManager The source’s Manager suffix makes this role explicit.
Feature data or observable state SourceModel The source’s Model suffix makes this role explicit.
Centralized state or persistence access ReminderStore The source’s Store suffix makes this role explicit.
User-interface presentation and input forwarding ContentView, MainView, MapView, WelcomeView The source’s View suffix makes this role explicit.

Design patterns

Pattern Source evidence Purpose or tradeoff
Delegate or data-source callbacks LocationBasedReminders/LocationManager.swift:33 Callback protocols invert event delivery back into the sample’s owner.
Central store LocationBasedReminders/ReminderStore.swift:28 A store-named type centralizes feature state or persistence.
Binding-based state propagation LocationBasedReminders/DeleteCompletedRemindersButton.swift:11 A binding exposes controlled read/write access while the upstream owner remains authoritative.
Actor isolation LocationBasedReminders/ReminderStore.swift:28 A declared actor creates an explicit isolation boundary; its executor is not described as a background thread.

Naming conventions

  • Types: App: LocationBasedRemindersApp; Manager: LocationManager, ReminderStoreManager; Model: SourceModel; Store: ReminderStore; View: ContentView, MainView, MapView, WelcomeView.
  • Protocols: no local protocol declaration in the scanned source.
  • Methods: requestAccess, defaultList, createReminder, save, saveList, ekReminder, fetchReminders, completeLocationReminder.
  • Files: LocationBasedReminders/LocationBasedRemindersApp.swift, LocationBasedReminders/ReminderStore.swift, LocationBasedReminders/ReminderStoreManager.swift, LocationBasedReminders/ContentView.swift, LocationBasedReminders/LocationManager.swift, LocationBasedReminders/MainView.swift.

Architecture takeaways

  • LocationBasedRemindersApp is the main source-visible entry or composition anchor for this sample.
  • Framework work reaches SwiftUI, EventKit, MapKit, CoreLocation 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
LocationBasedReminders/LocationBasedRemindersApp.swift Cited implementation, LocationBasedRemindersApp
LocationBasedReminders/ReminderStore.swift Cited implementation, ReminderStore, actor, ReminderStoreError
LocationBasedReminders/AppSettingsLink.swift Cited implementation, SwiftUI state property wrapper, EventKit, AppSettingsLink
LocationBasedReminders/LocationManager.swift Cited implementation, @MainActor, @Observable, OSLog, LocationManager
LocationBasedReminders/DeleteCompletedRemindersButton.swift Cited implementation, DeleteCompletedRemindersButton
LocationBasedReminders/ContentView.swift await suspension point, ContentView
LocationBasedReminders/DeleteConfirmationButton.swift Task, DeleteConfirmationButton
LocationBasedReminders/Geofence.swift Sendable or @Sendable, Geofence
LocationBasedReminders/ReminderStoreManager.swift NotificationCenter, ReminderStoreManagerError, ReminderStoreManager
LocationBasedReminders/AnnotationImage.swift SwiftUI, AnnotationImage
LocationBasedReminders/EKReminder+Extension.swift MapKit, Feature implementation
LocationBasedReminders/Helpers.swift Foundation, Feature implementation
LocationBasedReminders/MainView.swift MainView
LocationBasedReminders/MapView.swift MapView
LocationBasedReminders/SourceModel.swift SourceModel
LocationBasedReminders/WelcomeView.swift WelcomeView