swift-style

Name: swift-style
Author: johnrogers

Swift code style conventions for clean, readable, and idiomatic code. Enforces naming conventions (UpperCamelCase for types, lowerCamelCase for everything else) and prioritizes clarity over brevity Advocates the "golden path" pattern: early returns and guards to keep happy-path logic left-aligned, avoiding deep nesting Covers code organization with extensions and MARK comments, memory management with weak captures, and access control best practices Identifies five common mistakes: unnecessary abbreviations, nested conditionals, inconsistent self usage, vague type names, and implicit access control

INSTALLATION

npx skills add https://github.com/johnrogers/claude-swift-engineering --skill swift-style

Run in your project or agent environment. Adjust flags if your CLI version differs.

SKILL.md

Swift Style Guide

Code style conventions for clean, readable Swift code.

Core Principles

Clarity > Brevity > Consistency

Code should compile without warnings.

Naming

UpperCamelCase — Types, protocols

lowerCamelCase — Everything else

Clarity at call site

No abbreviations except universal (URL, ID)

// Preferred

let maximumWidgetCount = 100

func fetchUser(byID id: String) -> User

Golden Path

Left-hand margin is the happy path. Don't nest if statements.

// Preferred

func process(value: Int?) throws -> Result {

    guard let value = value else {

        throw ProcessError.nilValue

    }

    guard value > 0 else {

        throw ProcessError.invalidValue

    }

    return compute(value)

}

Code Organization

Use extensions and MARK comments:

class MyViewController: UIViewController {

    // Core implementation

}

// MARK: - UITableViewDataSource

extension MyViewController: UITableViewDataSource { }

Spacing

Braces open on same line, close on new line

One blank line between methods

Colon: no space before, one space after

Self

Avoid self unless required by compiler.

// Preferred

func configure() {

    backgroundColor = .systemBackground

}

Computed Properties

Omit get for read-only:

var diameter: Double {

    radius * 2

}

Closures

Trailing closure only for single closure parameter.

Type Inference

Let compiler infer when clear. For empty collections, use type annotation:

var names: [String] = []

Syntactic Sugar

// Preferred

var items: [String]

var cache: [String: Int]

var name: String?

Access Control

private over fileprivate

Don't add internal (it's the default)

Access control as leading specifier

Memory Management

resource.request().onComplete { [weak self] response in

    guard let self else { return }

    self.updateModel(response)

}

Comments

Explain why, not what

Use // or ///, avoid /* */

Keep up-to-date or delete

Constants

Use case-less enum for namespacing:

enum Math {

    static let pi = 3.14159

}

Common Mistakes

Abbreviations beyond URL, ID, UUID — Abbreviations like cfg, mgr, ctx, desc hurt readability. Spell them out: configuration, manager, context, description. The three exceptions are URL, ID, UUID.

Nested guard/if statements — Deep nesting makes code hard to follow. Use early returns and guards to keep the happy path left-aligned.

Inconsistent self usage — Either always omit self (preferred) or always use it. Mixing makes code scanning harder and confuses capture semantics.

Overly generic type names — Manager, Handler, Helper, Coordinator are too vague. Names should explain responsibility: PaymentProcessor, EventDispatcher, ImageCache, NavigationCoordinator.

Implied access control — Don't skip access control. Explicit private, public helps future maintainers understand module boundaries. internal is default, so omit it.