Initial commit: add all skills files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-10 16:52:49 +08:00
commit 6487becf60
396 changed files with 108871 additions and 0 deletions
--- a/ios-application-dev/references/swift-coding-standards.md
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+# Swift Coding Standards
+
+Best practices for writing clean, safe, and idiomatic Swift code following Apple's guidelines and modern Swift conventions.
+
+---
+
+## 1. Optionals and Safety
+
+**Impact:** CRITICAL
+
+Swift's optional system eliminates null pointer exceptions through compile-time safety.
+
+### 1.1 Safe Unwrapping with if let
+
+```swift
+if let name = optionalName {
+    print("Hello, \(name)")
+}
+
+// Multiple bindings
+if let name = userName, let age = userAge, age >= 18 {
+    print("\(name) is an adult")
+}
+```
+
+### 1.2 Guard for Early Exit
+
+Use `guard` to exit early when preconditions aren't met:
+
+```swift
+func processUser(_ user: User?) {
+    guard let user = user else { return }
+    guard !user.name.isEmpty else { return }
+    print(user.name)
+}
+```
+
+### 1.3 Nil Coalescing for Defaults
+
+```swift
+let displayName = name ?? "Anonymous"
+let count = items?.count ?? 0
+```
+
+### 1.4 Optional Chaining
+
+```swift
+let count = user?.profile?.posts?.count
+let uppercased = optionalString?.uppercased()
+```
+
+### 1.5 Optional map/flatMap
+
+```swift
+let uppercasedName = userName.map { $0.uppercased() }
+let userID = userIDString.flatMap { Int($0) }
+```
+
+### 1.6 Never Force Unwrap
+
+Avoid `!` force unwrapping. Use safe alternatives:
+
+| Instead of | Use |
+|------------|-----|
+| `value!` | `if let value = value { }` |
+| `array[0]` (unsafe) | `array.first` |
+| `dictionary["key"]!` | `dictionary["key", default: defaultValue]` |
+
+---
+
+## 2. Naming Conventions
+
+**Impact:** HIGH
+
+### 2.1 Types: PascalCase
+
+```swift
+class UserProfileViewController { }
+struct NetworkRequest { }
+protocol DataSource { }
+enum LoadingState { }
+```
+
+### 2.2 Variables and Functions: camelCase
+
+```swift
+var userName: String
+let maximumRetryCount = 3
+func fetchUserProfile() { }
+```
+
+### 2.3 Boolean Naming
+
+Use `is`, `has`, `should`, `can` prefixes:
+
+```swift
+var isLoading: Bool
+var hasCompletedOnboarding: Bool
+var shouldShowAlert: Bool
+var canEditProfile: Bool
+```
+
+### 2.4 Function Naming
+
+Use verb phrases, read like natural English:
+
+```swift
+// Good - clear actions
+func fetchUsers() async throws -> [User]
+func remove(_ item: Item, at index: Int)
+func makeIterator() -> Iterator
+
+// Avoid - unclear or redundant
+func getUsersData() // "get" is redundant
+func doRemove() // vague
+```
+
+### 2.5 Parameter Labels
+
+First parameter label can be omitted when obvious:
+
+```swift
+func insert(_ element: Element, at index: Int)
+func move(from source: Int, to destination: Int)
+```
+
+---
+
+## 3. Protocol-Oriented Design
+
+**Impact:** HIGH
+
+Swift favors composition over inheritance through protocols.
+
+### 3.1 Define Capabilities Through Protocols
+
+```swift
+protocol DataStore {
+    func save<T: Codable>(_ item: T, key: String) throws
+    func load<T: Codable>(key: String) throws -> T?
+}
+
+protocol Drawable {
+    var color: Color { get set }
+    func draw()
+}
+```
+
+### 3.2 Protocol Extensions for Default Behavior
+
+```swift
+extension Drawable {
+    func draw() {
+        print("Drawing with \(color)")
+    }
+}
+
+extension Collection {
+    func chunked(into size: Int) -> [[Element]] {
+        stride(from: 0, to: count, by: size).map {
+            Array(self[$0..<Swift.min($0 + size, count)])
+        }
+    }
+}
+```
+
+### 3.3 Associated Types for Flexibility
+
+```swift
+protocol Repository {
+    associatedtype Item
+    func fetchAll() async throws -> [Item]
+    func save(_ item: Item) async throws
+}
+
+class UserRepository: Repository {
+    typealias Item = User
+    
+    func fetchAll() async throws -> [User] { /* ... */ }
+    func save(_ item: User) async throws { /* ... */ }
+}
+```
+
+### 3.4 Protocol Composition
+
+```swift
+protocol Named { var name: String { get } }
+protocol Aged { var age: Int { get } }
+
+func greet(_ person: Named & Aged) {
+    print("Hello, \(person.name), age \(person.age)")
+}
+```
+
+---
+
+## 4. Value Types vs Reference Types
+
+**Impact:** HIGH
+
+### 4.1 Prefer Structs (Value Types)
+
+Use structs for simple data models, independent copies:
+
+```swift
+struct User {
+    var name: String
+    var email: String
+}
+
+struct Point {
+    var x: Double
+    var y: Double
+}
+```
+
+### 4.2 Use Classes When Needed
+
+Use classes for shared mutable state, identity matters:
+
+```swift
+class NetworkManager {
+    static let shared = NetworkManager()
+    private init() { }
+}
+
+class FileHandle {
+    // Wrapping system resource
+}
+```
+
+### 4.3 Enums for Finite States
+
+```swift
+enum LoadingState {
+    case idle
+    case loading
+    case success(Data)
+    case failure(Error)
+}
+
+enum Result<Success, Failure: Error> {
+    case success(Success)
+    case failure(Failure)
+}
+```
+
+| Type | Use When |
+|------|----------|
+| `struct` | Data models, coordinates, independent values |
+| `class` | Shared state, identity matters, inheritance needed |
+| `enum` | Finite set of options, state machines |
+
+---
+
+## 5. Memory Management with ARC
+
+**Impact:** CRITICAL
+
+### 5.1 Breaking Retain Cycles with weak
+
+```swift
+class Apartment {
+    weak var tenant: Person?
+}
+
+class Person {
+    var apartment: Apartment?
+}
+```
+
+### 5.2 Closure Capture Lists
+
+```swift
+// Weak capture for optional self
+onComplete = { [weak self] in
+    self?.processResult()
+}
+
+// Capture specific values
+let id = user.id
+fetchData { [id] result in
+    print("Fetched for \(id)")
+}
+```
+
+### 5.3 unowned for Guaranteed Lifetime
+
+Use when reference should never be nil during object lifetime:
+
+```swift
+class CreditCard {
+    unowned let customer: Customer
+    
+    init(customer: Customer) {
+        self.customer = customer
+    }
+}
+```
+
+| Keyword | Use When |
+|---------|----------|
+| `weak` | Reference may become nil |
+| `unowned` | Reference guaranteed to outlive |
+| None | Strong ownership needed |
+
+---
+
+## 6. Error Handling
+
+**Impact:** HIGH
+
+### 6.1 Define Typed Errors
+
+```swift
+enum NetworkError: Error {
+    case invalidURL
+    case noConnection
+    case serverError(statusCode: Int)
+    case decodingFailed(underlying: Error)
+}
+
+enum ValidationError: LocalizedError {
+    case emptyField(name: String)
+    case invalidFormat(field: String, expected: String)
+    
+    var errorDescription: String? {
+        switch self {
+        case .emptyField(let name):
+            return "\(name) cannot be empty"
+        case .invalidFormat(let field, let expected):
+            return "\(field) must be \(expected)"
+        }
+    }
+}
+```
+
+### 6.2 Throwing Functions
+
+```swift
+func fetchUser(id: Int) throws -> User {
+    guard let url = URL(string: "https://api.example.com/users/\(id)") else {
+        throw NetworkError.invalidURL
+    }
+    // ... implementation
+}
+```
+
+### 6.3 Do-Catch Handling
+
+```swift
+do {
+    let user = try fetchUser(id: 123)
+    print(user.name)
+} catch NetworkError.serverError(let code) {
+    print("Server error: \(code)")
+} catch NetworkError.noConnection {
+    print("Check your internet connection")
+} catch {
+    print("Unknown error: \(error)")
+}
+```
+
+### 6.4 try? and try!
+
+```swift
+// try? returns optional (nil on error)
+let user = try? fetchUser(id: 123)
+
+// try! crashes on error - use only when failure is programmer error
+let config = try! loadBundledConfig()
+```
+
+### 6.5 Rethrows
+
+```swift
+func perform<T>(_ operation: () throws -> T) rethrows -> T {
+    return try operation()
+}
+```
+
+---
+
+## 7. Modern Concurrency (async/await)
+
+**Impact:** CRITICAL
+
+### 7.1 Async Functions
+
+```swift
+func fetchUser(id: Int) async throws -> User {
+    guard let url = URL(string: "https://api.example.com/users/\(id)") else {
+        throw NetworkError.invalidURL
+    }
+    let (data, _) = try await URLSession.shared.data(from: url)
+    return try JSONDecoder().decode(User.self, from: data)
+}
+
+// Calling async functions
+Task {
+    do {
+        let user = try await fetchUser(id: 123)
+        print(user.name)
+    } catch {
+        print("Failed: \(error)")
+    }
+}
+```
+
+### 7.2 Parallel Execution with TaskGroup
+
+```swift
+func fetchAllUsers(ids: [Int]) async throws -> [User] {
+    try await withThrowingTaskGroup(of: User.self) { group in
+        for id in ids {
+            group.addTask {
+                try await fetchUser(id: id)
+            }
+        }
+        return try await group.reduce(into: []) { $0.append($1) }
+    }
+}
+```
+
+### 7.3 async let for Concurrent Bindings
+
+```swift
+async let user = fetchUser(id: 1)
+async let posts = fetchPosts(userId: 1)
+async let followers = fetchFollowers(userId: 1)
+
+let profile = try await ProfileData(
+    user: user,
+    posts: posts,
+    followers: followers
+)
+```
+
+### 7.4 Actors for Thread-Safe State
+
+```swift
+actor BankAccount {
+    private var balance: Double = 0
+    
+    func deposit(_ amount: Double) {
+        balance += amount
+    }
+    
+    func withdraw(_ amount: Double) throws {
+        guard balance >= amount else {
+            throw BankError.insufficientFunds
+        }
+        balance -= amount
+    }
+    
+    func getBalance() -> Double {
+        balance
+    }
+}
+
+// Usage
+let account = BankAccount()
+await account.deposit(100)
+let balance = await account.getBalance()
+```
+
+### 7.5 MainActor for UI Updates
+
+```swift
+@MainActor
+class ViewModel: ObservableObject {
+    @Published var isLoading = false
+    @Published var users: [User] = []
+    
+    func loadUsers() async {
+        isLoading = true
+        defer { isLoading = false }
+        
+        do {
+            users = try await fetchUsers()
+        } catch {
+            // Handle error
+        }
+    }
+}
+```
+
+### 7.6 Task Cancellation
+
+```swift
+func fetchWithTimeout() async throws -> Data {
+    try await withThrowingTaskGroup(of: Data.self) { group in
+        group.addTask {
+            try await fetchData()
+        }
+        group.addTask {
+            try await Task.sleep(for: .seconds(10))
+            throw TimeoutError()
+        }
+        
+        let result = try await group.next()!
+        group.cancelAll()
+        return result
+    }
+}
+
+// Check for cancellation
+func longOperation() async throws {
+    for item in items {
+        try Task.checkCancellation()
+        await process(item)
+    }
+}
+```
+
+---
+
+## 8. Access Control
+
+**Impact:** MEDIUM
+
+### 8.1 Access Levels
+
+| Level | Scope |
+|-------|-------|
+| `private` | Enclosing declaration only |
+| `fileprivate` | Entire source file |
+| `internal` | Module (default) |
+| `public` | Other modules can access |
+| `open` | Other modules can subclass/override |
+
+### 8.2 Best Practices
+
+```swift
+public class UserService {
+    // Public API
+    public func fetchUser(id: Int) async throws -> User { }
+    
+    // Internal helper
+    func buildRequest(for id: Int) -> URLRequest { }
+    
+    // Private implementation detail
+    private let session: URLSession
+    private var cache: [Int: User] = [:]
+}
+```
+
+### 8.3 Private Setters
+
+```swift
+public struct Counter {
+    public private(set) var count = 0
+    
+    public mutating func increment() {
+        count += 1
+    }
+}
+```
+
+---
+
+## 9. Generics and Type Constraints
+
+**Impact:** MEDIUM
+
+### 9.1 Generic Functions
+
+```swift
+func swapValues<T>(_ a: inout T, _ b: inout T) {
+    let temp = a
+    a = b
+    b = temp
+}
+```
+
+### 9.2 Type Constraints
+
+```swift
+func findIndex<T: Equatable>(of value: T, in array: [T]) -> Int? {
+    array.firstIndex(of: value)
+}
+
+func decode<T: Decodable>(_ type: T.Type, from data: Data) throws -> T {
+    try JSONDecoder().decode(type, from: data)
+}
+```
+
+### 9.3 Where Clauses
+
+```swift
+func allMatch<C: Collection>(_ collection: C, predicate: (C.Element) -> Bool) -> Bool
+    where C.Element: Equatable {
+    collection.allSatisfy(predicate)
+}
+
+extension Array where Element: Numeric {
+    func sum() -> Element {
+        reduce(0, +)
+    }
+}
+```
+
+### 9.4 Opaque Types (some)
+
+```swift
+func makeCollection() -> some Collection {
+    [1, 2, 3]
+}
+
+var body: some View {
+    Text("Hello")
+}
+```
+
+---
+
+## 10. Property Wrappers
+
+**Impact:** MEDIUM
+
+### 10.1 Common SwiftUI Property Wrappers
+
+| Wrapper | Use Case |
+|---------|----------|
+| `@State` | View-local mutable state |
+| `@Binding` | Two-way connection to parent state |
+| `@StateObject` | View-owned observable object |
+| `@ObservedObject` | Passed-in observable object |
+| `@EnvironmentObject` | Shared object from ancestor |
+| `@Environment` | System environment values |
+| `@Published` | Observable property in class |
+
+### 10.2 Custom Property Wrappers
+
+```swift
+@propertyWrapper
+struct Clamped<Value: Comparable> {
+    private var value: Value
+    let 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)
+    }
+}
+
+struct Settings {
+    @Clamped(0...100) var volume: Int = 50
+}
+```
+
+---
+
+## Quick Reference
+
+### Optionals
+
+```swift
+if let x = optional { }      // Safe unwrap
+guard let x = optional else { return }  // Early exit
+let x = optional ?? default  // Default value
+optional?.method()           // Optional chaining
+optional.map { transform($0) }  // Transform if present
+```
+
+### Common Patterns
+
+```swift
+// Defer for cleanup
+func process() {
+    let file = openFile()
+    defer { closeFile(file) }
+    // ... work with file
+}
+
+// Lazy initialization
+lazy var expensive: ExpensiveObject = {
+    ExpensiveObject()
+}()
+
+// Type inference
+let numbers = [1, 2, 3]  // [Int]
+let doubled = numbers.map { $0 * 2 }  // [Int]
+```
+
+### Closure Syntax
+
+```swift
+// Full syntax
+let sorted = names.sorted(by: { (s1: String, s2: String) -> Bool in
+    return s1 < s2
+})
+
+// Shortened
+let sorted = names.sorted { $0 < $1 }
+
+// Trailing closure
+UIView.animate(withDuration: 0.3) {
+    view.alpha = 0
+}
+```
+
+---
+
+## Checklist
+
+### Safety
+- [ ] No force unwrapping (`!`) except for IB outlets and known-safe cases
+- [ ] All optionals handled with `if let`, `guard let`, or `??`
+- [ ] No implicitly unwrapped optionals (`!`) in data models
+
+### Memory
+- [ ] Closures use `[weak self]` when capturing self in escaping closures
+- [ ] Delegate properties are `weak`
+- [ ] No retain cycles between objects
+
+### Concurrency
+- [ ] Async functions used instead of completion handlers
+- [ ] Actors protect shared mutable state
+- [ ] UI updates on `@MainActor`
+- [ ] Task cancellation checked in long operations
+
+### Access Control
+- [ ] `private` used for implementation details
+- [ ] `public` API is minimal and intentional
+- [ ] No unnecessary `internal` exposure
+
+### Naming
+- [ ] Types use PascalCase
+- [ ] Functions and variables use camelCase
+- [ ] Booleans have `is`/`has`/`should` prefix
+- [ ] Functions read like natural English
+
+---
+
+*Swift and Apple are trademarks of Apple Inc.*