Using the Bloom filter tool to configure a URL filter

At a glance

Project structure

Source bundle/
├── SimpleURLFilter/
│   ├── SimpleURLFilter/
│   │   ├── SimpleURLFilterApp.swift
│   │   ├── View Models/
│   │   │   └── ContentViewModel.swift
│   │   ├── Views/
│   │   │   ├── ConfigurationView.swift
│   │   │   └── ContentView.swift
│   │   └── Model/
│   │       ├── ConfigurationModel.swift
│   │       ├── ActivityState.swift
│   │       ├── Configuration.swift
│   │       └── FilterStatus.swift
│   └── SimpleURLFilterExtension/
│       └── URLFilterControlProvider.swift
├── BloomFilterTool/
│   └── BloomFilterTool/
│       ├── BloomFilterTool.swift
│       └── pir_database.pb.swift
└── SwiftBloomFilter/
    └── SwiftBloomFilter/
        └── BloomFilter.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Shell, Swift.
• The verified tree contains 12 project/configuration file(s) and 30 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["BloomFilterTool"]
    V2["SimpleURLFilter"]
    Boundary["NetworkExtension APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary

Reference code

SimpleURLFilter/SimpleURLFilter/SimpleURLFilterApp.swift:11 — architecture anchor

@main
struct SimpleURLFilterApp: App {
    @Environment(\.scenePhase) private var scenePhase
    // ...
}

Interpretation

The branches represent separate entry-bearing project variants in the downloaded bundle, not runtime calls between those variants. Each branch is intentionally collapsed at the documented framework boundary; the detailed target-local flow remains in the cited files. Ownership is claimed only where the next section cites a stored property or assignment.

Ownership and state

classDiagram
    SimpleURLFilterApp *-- ConfigurationModel : configurationModel
    SimpleURLFilterApp *-- ContentViewModel : viewModel
    URLFilterControlProvider o-- BloomFilter : filter
    URLFilterControlProvider o-- Logger : log

Ownership evidence

SimpleURLFilter/SimpleURLFilter/SimpleURLFilterApp.swift:14 — stored dependency or nearest verified ownership anchor

@main
struct SimpleURLFilterApp: App {
    // ...
    @State private var configurationModel: ConfigurationModel
    // ...
}

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

BloomFilterTool/BloomFilterTool/BloomFilterTool.swift:53 — representative execution boundary

    mutating func run() async throws {
        // ...
        if filterOutputFile == nil {
            filterOutputFile = URL.currentDirectory().appending(path: BloomFilterToolDefaults.filterOutputFileName)
        }
        // ...
    }

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

SimpleURLFilter/SimpleURLFilter/SimpleURLFilterApp.swift:12 — representative type boundary

@main
struct SimpleURLFilterApp: App {
    @Environment(\.scenePhase) private var scenePhase
    // ...
}

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

Access control

Reference code

BloomFilterTool/BloomFilterTool/pir_database.pb.swift:78 — representative boundary

fileprivate let _protobuf_package = "apple.swift_homomorphic_encryption.pir.v1"

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: SimpleURLFilterApp; Model: ConfigurationModel; Provider: URLFilterControlProvider; View: ConfigurationView, ContentView; ViewModel: ContentViewModel.
• Protocols: no local protocol declaration in the scanned source.
• Methods: content, loadBloomFilter, filterTag, start, stop, fetchPrefilter, run, readTo.
• Files: SimpleURLFilter/SimpleURLFilter/SimpleURLFilterApp.swift, SimpleURLFilter/SimpleURLFilterExtension/URLFilterControlProvider.swift, BloomFilterTool/BloomFilterTool/BloomFilterTool.swift, SimpleURLFilter/SimpleURLFilter/View Models/ContentViewModel.swift, SimpleURLFilter/SimpleURLFilter/Views/ConfigurationView.swift, SimpleURLFilter/SimpleURLFilter/Model/ConfigurationModel.swift.

Architecture takeaways

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