Building a Custom Catalog and Matching Audio

At a glance

Project structure

Source bundle/
├── Shared Source/
│   ├── App/
│   │   ├── FoodMathApp.swift
│   │   └── ContentView.swift
│   ├── Views/
│   │   ├── QuestionView.swift
│   │   ├── EpisodeListView.swift
│   │   ├── EpisodeView.swift
│   │   ├── CardView.swift
│   │   ├── NumberPadView.swift
│   │   └── BlurView.swift
│   └── Data/
│       └── Equation.swift
├── Part 1 - Matching Audio/
│   └── FoodMath/
│       └── CatalogProvider.swift
├── Part 2 - Content Synchronization/
│   └── FoodMath/
│       └── CatalogProvider.swift
└── Part 3 - Final/
    └── FoodMath/
        └── CatalogProvider.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 10 project/configuration file(s) and 31 source declaration(s).

Overall architecture

flowchart LR
    N1["FoodMathApp"]
    N2["ContentView"]
    N3["CatalogProvider"]
    N4["ShazamKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

Shared Source/App/FoodMathApp.swift:10 — architecture anchor

@main
struct FoodMathApp: App {
    @StateObject private var matcher = Matcher()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(matcher)
        }
    }
}

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 ShazamKit.

Ownership and state

classDiagram
    FoodMathApp *-- Matcher : matcher
    QuestionView o-- Equation : equation
    AppleGridView o-- EquationType : equation
    AppleGridView o-- Rows : rows

Ownership evidence

Shared Source/App/FoodMathApp.swift:12 — stored dependency or nearest verified ownership anchor

@main
struct FoodMathApp: App {
    @StateObject private var matcher = Matcher()
    // ...
}

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

Part 1 - Matching Audio/FoodMath/Matcher.swift:46 — representative execution boundary

        DispatchQueue.main.async {
            self.result = MatchResult(mediaItem: match.mediaItems.first, question: nil)
        }

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

Shared Source/App/FoodMathApp.swift:11 — representative type boundary

@main
struct FoodMathApp: App {
    @StateObject private var matcher = Matcher()
    // ...
}

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

Access control

Reference code

Part 1 - Matching Audio/FoodMath/Matcher.swift:24 — representative boundary

class Matcher: NSObject, ObservableObject, SHSessionDelegate {
    // ...
    private var session: SHSession?
    // ...
}

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

The final target’s audio-matching path crosses UI, catalog construction, microphone capture, and ShazamKit delegate delivery, so the callback order is easier to verify as a sequence.

sequenceDiagram
    actor User
    participant View as ContentView
    participant Catalog as CatalogProvider
    participant Matcher
    participant Audio as AVAudioEngine
    participant Shazam as SHSession
    User->>View: Open lesson
    View->>Catalog: catalog()
    Catalog-->>View: SHCustomCatalog
    View->>Matcher: match(catalog)
    Matcher->>Shazam: Create session and set delegate
    Matcher->>Audio: Install input tap and request permission
    Audio-->>Shazam: matchStreamingBuffer(buffer, time)
    Shazam-->>Matcher: session(didFind:)
    Matcher-->>View: Publish MatchResult on main queue

Reference code

Part 3 - Final/FoodMath/Matcher.swift:27 — match

    func match(catalog: SHCustomCatalog) throws {

        session = SHSession(catalog: catalog)
        session?.delegate = self

        let audioFormat = AVAudioFormat(standardFormatWithSampleRate: audioEngine.inputNode.outputFormat(forBus: 0).sampleRate,
                                        channels: 1)
        audioEngine.inputNode.installTap(onBus: 0, bufferSize: 2048, format: audioFormat) { [weak session] buffer, audioTime in
            session?.matchStreamingBuffer(buffer, at: audioTime)
        }

        try AVAudioSession.sharedInstance().setCategory(.record)
        AVAudioSession.sharedInstance().requestRecordPermission { [weak self] success in
            guard success, let self = self else { return }
            try? self.audioEngine.start()
        }
    }

Naming conventions

• Types: App: FoodMathApp; Operation: EquationOperation; Provider: CatalogProvider; View: AppleGridView, AppleGroupView, BackgroundView, BoardView, CardView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: onSelect, catalog.
• Files: Shared Source/App/FoodMathApp.swift, Shared Source/Views/QuestionView.swift, Shared Source/Views/EpisodeListView.swift, Shared Source/Views/EpisodeView.swift, Shared Source/App/ContentView.swift, Shared Source/Views/CardView.swift.

Architecture takeaways

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