Fetching weather forecasts with WeatherKit

At a glance

Project structure

Source bundle/
└── FlightPlanner/
    ├── FlightPlannerApp.swift
    ├── Models/
    │   ├── FlightLegGenerator.swift
    │   ├── FlightSegmentGenerator.swift
    │   ├── Airport.swift
    │   ├── AirportData.swift
    │   ├── FlightData.swift
    │   └── FlightForecastInfo.swift
    └── Views/
        ├── BookingForm/
        │   ├── BookingFormAirportDetails.swift
        │   └── BookingFormDateDetails.swift
        ├── ContentView.swift
        ├── FlightItineraryList/
        │   └── FlightLegRowHeader.swift
        └── FlightLegDetail/
            └── FlightLegDetailWeatherGrid.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 55 source declaration(s).

Overall architecture

flowchart LR
    N1["FlightPlannerApp"]
    N2["ContentView"]
    N3["Store"]
    N4["FlightLegGenerator"]
    N5["WeatherKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

FlightPlanner/FlightPlannerApp.swift:11 — architecture anchor

@main
struct FlightPlannerApp: 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 WeatherKit.

Ownership and state

classDiagram
    BookingFormAirportDetails *-- Array : airports
    BookingFormAirportDetails o-- Airport : origin
    BookingFormAirportDetails o-- Airport : destination
    BookingFormAirportDetails o-- FlightJourney : journey

Ownership evidence

FlightPlanner/Views/BookingForm/BookingFormAirportDetails.swift:12 — stored dependency or nearest verified ownership anchor

struct BookingFormAirportDetails: View {
    var airports: [Airport]
    // ...
}

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.

@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

FlightPlanner/Models/AirportData.swift:11 — representative execution boundary

@MainActor
class AirportData: ObservableObject {
    let logger = Logger(subsystem: "com.example.apple-samplecode.FlightPlanner.AirportData", category: "Model")
    // ...
}

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.

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

FlightPlanner/FlightPlannerApp.swift:12 — representative type boundary

@main
struct FlightPlannerApp: App {
    // ...
            ContentView()
    // ...
}

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

Access control

Reference code

FlightPlanner/Models/Airport.swift:56 — representative boundary

    fileprivate static func randomImageName(for airport: Airport) -> String {
        // ...
        let sum = airport.elevation + airport.latitude + airport.longitude
        // ...
    }

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: App: FlightPlannerApp; Generator: FlightLegGenerator, FlightSegmentGenerator, SeededRandomNumberGenerator; Store: Store; View: ContentView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: makeLeg, makeDeparture, makeArrival, segment, onDelete, randomImageName, next, makeBody.
• Files: FlightPlanner/FlightPlannerApp.swift, FlightPlanner/Models/FlightLegGenerator.swift, FlightPlanner/Models/FlightSegmentGenerator.swift, FlightPlanner/Views/BookingForm/BookingFormAirportDetails.swift, FlightPlanner/Views/ContentView.swift, FlightPlanner/Models/Airport.swift.

Architecture takeaways

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

• Official Apple documentation