Swift language guardrails, patterns, and best practices for AI-assisted development.
Use when working with Swift files (.swift), Package.swift, or when the user mentions Swift.
Provides optionals handling, protocol-oriented patterns, concurrency with async/await,
and testing standards specific to this project's coding standards.
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Swift language guardrails, patterns, and best practices for AI-assisted development.
Use when working with Swift files (.swift), Package.swift, or when the user mentions Swift.
Provides optionals handling, protocol-oriented patterns, concurrency with async/await,
and testing standards specific to this project's coding standards.
protocolTimestamped {
var createdAt: Date { get }
var updatedAt: Date { get }
}
extensionTimestamped {
var isRecent: Bool { updatedAt.timeIntervalSinceNow >-86_400 }
}
// Protocol composition for flexible constraintsfuncfindRecent<T: Identifiable & Timestamped>(_items: [T]) -> [T] {
items.filter(\.isRecent)
}
funcfetchAllUsers(ids: [String]) asyncthrows -> [User] {
tryawait withThrowingTaskGroup(of: User.self) { group infor id in ids {
group.addTask { tryawaitself.fetchUser(id: id) }
}
var users: [User] = []
fortryawait user in group { users.append(user) }
return users
}
}
Sendable Conformance
// Value types: implicitly Sendable when all stored properties are SendablestructUserDTO: Sendable { let id: String; let name: String }
// Classes: must be final with immutable properties, or use @unchecked with a lockfinalclassAppConfig: Sendable { let apiBaseURL: URL; let maxRetries: Intinit(apiBaseURL: URL, maxRetries: Int=3) { self.apiBaseURL = apiBaseURL; self.maxRetries = maxRetries }
}
Property Wrappers
@propertyWrapperstructClamped<Value: Comparable> {
privatevar value: Valueprivatelet range: ClosedRange<Value>
var wrappedValue: Value {
get { value }
set { value =min(max(newValue, range.lowerBound), range.upperBound) }
}
init(wrappedValue: Value, _range: ClosedRange<Value>) {
self.range = range
self.value =min(max(wrappedValue, range.lowerBound), range.upperBound)
}
}
structAudioSettings {
@Clamped(0...100) var volume: Int=50@Clamped(0.5...2.0) var playbackSpeed: Double=1.0
}
Test names describe behavior: func test_login_withExpiredToken_refreshesAutomatically()
Use setUp() / tearDown() for shared test fixtures
Use protocol-based mocks injected via initializer (no singletons)
Async tests use async throws directly (no XCTestExpectation for async/await code)
Coverage target: >80% for business logic, >60% overall
Test both success and failure paths for every public method
Tooling
Essential Commands
swift build # Build all targets
swift test# Run all tests
swift test --enable-code-coverage # With coverage
swift package resolve # Resolve dependencies
swift package update # Update dependencies
swift format . # Format (swift-format)
swiftlint # Lint (SwiftLint)
swiftlint --fix # Auto-fix lint issues
SwiftLint Key Rules
# .swiftlint.yml -- enforce these as errorsforce_cast:errorforce_unwrapping:errorforce_try:errorfunction_body_length:warning:40error:50cyclomatic_complexity:warning:8error:10
