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

Configuring your app to use alternate app icons

At a glance

Item Summary
Purpose Add alternate app icons to your app, and let people choose which icon to display.
App architecture A Swift sample with the source-visible chain AlternateAppIconContentViewModelSwiftUI / UIKit APIs.
Main patterns SwiftUI environment injection
Project style 5 scanned source file(s) across Swift, organized around ranked entry, type, and file boundaries.
Execution model Source-visible boundaries: @MainActor; none alone proves a background thread.
State/event model Source-visible mechanisms: SwiftUI state property wrapper, @Observable.
Key frameworks/packages SwiftUI, OSLog, UIKit; these are source dependencies, not architecture labels.

Project structure

Source bundle/
├── AlternateAppIcon/
│   ├── AlternateAppIcon.swift
│   ├── ContentView.swift
│   ├── Model.swift
│   ├── Icon.swift
│   └── IconChooser.swift
├── AlternateAppIcon.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 3 project/configuration file(s) and 5 source declaration(s).

Overall architecture

Reference code

AlternateAppIcon/AlternateAppIcon.swift:10 — architecture anchor

@main
struct AlternateAppIcon: 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 Xcode.

Ownership and state

Ownership evidence

AlternateAppIcon/ContentView.swift:11 — stored dependency or nearest verified ownership anchor

struct ContentView: View {
    @State private var model = Model()
    // ...
}
Owner Object or state Relationship Mutation authority
ContentView Model (model) owns wrapper-managed state Owning lexical scope
Model Icon (appIcon) stores or receives App/module collaborators
Model Logger (logger) creates and retains Initialized by the owner; the binding is immutable
IconChooser Model (model) receives environment-provided state The environment provider is authoritative

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
Main isolation @MainActor The cited annotation marks its attached declaration or closure as main-actor isolated. AlternateAppIcon/Model.swift:12

@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

AlternateAppIcon/Model.swift:12 — representative execution boundary

@MainActor
@Observable class Model {
    var appIcon: Icon
    // ...
}

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. AlternateAppIcon/ContentView.swift:11
State propagation @Observable Observation macro publishes source-visible changes. AlternateAppIcon/Model.swift:13
Source import SwiftUI The cited file imports this module; runtime use and architectural role are not inferred. AlternateAppIcon/AlternateAppIcon.swift:8
Source import OSLog The cited file imports this module; runtime use and architectural role are not inferred. AlternateAppIcon/Model.swift:10
Source import UIKit The cited file imports this module; runtime use and architectural role are not inferred. AlternateAppIcon/Model.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

AlternateAppIcon/ContentView.swift:10 — representative type boundary

struct ContentView: View {
    @State private var model = Model()
    // ...
}
Type Responsibility Depends on or conforms to
ContentView User-interface presentation and input forwarding View
Model Feature data or observable state Concrete collaborators/imported frameworks
AlternateAppIcon Represents a feature value or composable behavior App
Icon Defines a closed set of feature states or choices String, CaseIterable, Identifiable
IconChooser Represents a feature value or composable behavior View

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
model (AlternateAppIcon/ContentView.swift:11) 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.
columns (AlternateAppIcon/IconChooser.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.
logger (AlternateAppIcon/Model.swift:15) 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

AlternateAppIcon/ContentView.swift:11 — representative boundary

struct ContentView: View {
    @State private var model = Model()
    // ...
}

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
Feature data or observable state Model The source’s Model suffix makes this role explicit.
User-interface presentation and input forwarding ContentView The source’s View suffix makes this role explicit.

Design patterns

Pattern Source evidence Purpose or tradeoff
SwiftUI environment injection AlternateAppIcon/IconChooser.swift:11 The environment supplies state or a capability without threading it through every initializer.

Naming conventions

  • Types: Model: Model; View: ContentView.
  • Protocols: no local protocol declaration in the scanned source.
  • Methods: setAlternateAppIcon.
  • Files: AlternateAppIcon/AlternateAppIcon.swift, AlternateAppIcon/ContentView.swift, AlternateAppIcon/Model.swift, AlternateAppIcon/Icon.swift, AlternateAppIcon/IconChooser.swift.

Architecture takeaways

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

Source file Relevant symbols
AlternateAppIcon/AlternateAppIcon.swift Cited implementation, SwiftUI, AlternateAppIcon
AlternateAppIcon/ContentView.swift Cited implementation, ContentView, SwiftUI state property wrapper
AlternateAppIcon/IconChooser.swift Cited implementation, IconChooser
AlternateAppIcon/Model.swift Cited implementation, @MainActor, @Observable, OSLog, UIKit, Model
AlternateAppIcon/Icon.swift Icon