HoRain云--Swift类全面解析：从基础到实战

HoRain 云小助手个人主页⛺️生活的理想就是为了理想的生活!⛳️ 推荐前些天发现了一个超棒的服务器购买网站性价比超高大内存超划算忍不住分享一下给大家。点击跳转到网站。目录⛳️ 推荐Swift 类Class一、类的基本定义1. 基本语法2. 示例定义一个简单的类二、类的核心特性1. 引用类型特性2. 继承3. 多态和类型转换三、类的高级特性1. 属性观察器2. 静态成员3. 可失败构造器4. 必要构造器四、内存管理 - ARC自动引用计数1. 强引用2. 弱引用和无主引用五、类 vs 结构体六、何时使用类七、最佳实践八、实际应用示例1. MVC 架构中的模型类2. 网络服务管理器3. 观察者模式实现Swift 类ClassSwift 类是一种引用类型的复合数据类型用于定义具有属性、方法、构造器等的蓝图。与结构体不同类支持继承、类型转换、析构器等面向对象特性。一、类的基本定义1. 基本语法class 类名 { // 存储属性 var 属性1: 类型 let 属性2: 类型 // 计算属性 var 计算属性: 类型 { get { // 返回值 } set { // 设置新值 } } // 方法 func 方法名(参数) - 返回类型 { // 方法实现 } // 构造器 init(参数) { // 初始化代码 } // 析构器 deinit { // 清理代码 } }2. 示例定义一个简单的类class Person { // 存储属性 var name: String var age: Int let gender: String // 计算属性 var description: String { return \(name) is \(age) years old, gender: \(gender) } // 构造器 init(name: String, age: Int, gender: String) { self.name name self.age age self.gender gender } // 方法 func celebrateBirthday() { age 1 print(\(name) is now \(age) years old!) } // 析构器 deinit { print(\(name) is being deallocated) } }二、类的核心特性1. 引用类型特性let person1 Person(name: John, age: 25, gender: Male) let person2 person1 // person2 指向同一个实例 person2.name Jane print(person1.name) // 输出: Jane (person1 也被修改) print(person1 person2) // true指向同一个实例2. 继承class Student: Person { var studentID: String var grade: String // 重写父类属性 override var description: String { return super.description , Student ID: \(studentID), Grade: \(grade) } // 便利构造器 convenience init(name: String, age: Int, studentID: String, grade: String) { self.init(name: name, age: age, gender: Unknown, studentID: studentID, grade: grade) } // 指定构造器 init(name: String, age: Int, gender: String, studentID: String, grade: String) { self.studentID studentID self.grade grade super.init(name: name, age: age, gender: gender) } // 重写父类方法 override func celebrateBirthday() { super.celebrateBirthday() print(\(name) got a birthday gift from school!) } }3. 多态和类型转换class Teacher: Person { var subject: String init(name: String, age: Int, gender: String, subject: String) { self.subject subject super.init(name: name, age: age, gender: gender) } override var description: String { return super.description , teaches \(subject) } } // 多态示例 var people: [Person] [ Student(name: Alice, age: 18, gender: Female, studentID: S001, grade: A), Teacher(name: Bob, age: 35, gender: Male, subject: Math) ] for person in people { print(person.description) // 根据类型进行转换 if let student person as? Student { print(Student ID: \(student.studentID)) } else if let teacher person as? Teacher { print(Subject: \(teacher.subject)) } }三、类的高级特性1. 属性观察器class BankAccount { var balance: Double 0.0 { willSet(newBalance) { print(Balance will change from \(balance) to \(newBalance)) } didSet { if balance 0 { print(Warning: Negative balance!) } } } init(initialBalance: Double) { balance initialBalance } }2. 静态成员class MathUtils { static let pi 3.14159265359 static let e 2.71828182846 static func square(_ number: Double) - Double { return number * number } class func cube(_ number: Double) - Double { return number * number * number } } print(MathUtils.pi) // 3.14159265359 print(MathUtils.square(5)) // 25.0 print(MathUtils.cube(3)) // 27.03. 可失败构造器class Product { let id: String let name: String let price: Double init?(id: String, name: String, price: Double) { guard price 0 else { return nil // 价格不能为负数 } self.id id self.name name self.price price } } if let product Product(id: P001, name: iPhone, price: 999.99) { print(Product created: \(product.name)) } else { print(Failed to create product) }4. 必要构造器class Vehicle { var numberOfWheels: Int required init(numberOfWheels: Int) { self.numberOfWheels numberOfWheels } } class Car: Vehicle { var brand: String required init(numberOfWheels: Int) { brand Unknown super.init(numberOfWheels: numberOfWheels) } init(brand: String, numberOfWheels: Int) { self.brand brand super.init(numberOfWheels: numberOfWheels) } }四、内存管理 - ARC自动引用计数1. 强引用class Apartment { let number: Int var tenant: Person? init(number: Int) { self.number number } deinit { print(Apartment #\(number) is being deallocated) } } var john: Person? Person(name: John, age: 25, gender: Male) var apartment101: Apartment? Apartment(number: 101) apartment101?.tenant john john nil // 不会释放因为apartment101还持有引用2. 弱引用和无主引用class Customer { let name: String var apartment: Apartment? init(name: String) { self.name name } deinit { print(\(name) is being deallocated) } } class ApartmentWithWeakRef { let number: Int weak var tenant: Customer? // 弱引用不增加引用计数 init(number: Int) { self.number number } deinit { print(Apartment #\(number) is being deallocated) } } var alice: Customer? Customer(name: Alice) var apartment202: ApartmentWithWeakRef? ApartmentWithWeakRef(number: 202) apartment202?.tenant alice alice nil // 释放Customer因为弱引用不阻止释放 apartment202 nil // 释放Apartment五、类 vs 结构体特性类结构体类型引用类型值类型继承支持不支持类型转换支持运行时检查不支持析构器支持deinit不支持引用计数有 ARC 管理无mutating 方法不需要mutating需要mutating内存分配堆分配栈分配通常性能通常较慢通常更快共享状态多个引用共享同一实例每个变量有自己的拷贝六、何时使用类推荐使用类的场景需要继承和多态需要引用语义多个引用指向同一实例需要析构器进行资源清理需要 Objective-C 互操作需要类型转换如as?,is处理复杂对象图避免大量拷贝推荐使用结构体的场景数据相对简单且独立需要值语义拷贝而非共享性能敏感的场景不需要继承通常作为数据模型七、最佳实践优先使用值类型除非需要类的特性否则优先选择结构体避免循环引用使用weak或unowned打破强引用循环封装良好使用private、fileprivate等访问控制修饰符构造器设计提供便利构造器简化初始化协议导向优先使用协议而非继承来共享行为内存安全确保无主引用始终有值避免悬垂指针单一职责每个类应该只有一个职责避免上帝对象八、实际应用示例1. MVC 架构中的模型类class UserModel { private(set) var id: UUID private(set) var username: String private(set) var email: String private(set) var createdAt: Date var displayName: String { return username } init(username: String, email: String) { self.id UUID() self.username username self.email email self.createdAt Date() } func updateUsername(_ newUsername: String) { guard !newUsername.isEmpty else { return } username newUsername } }2. 网络服务管理器class NetworkManager { static let shared NetworkManager() private let baseURL https://api.example.com private let session URLSession.shared private init() {} func fetchDataT: Decodable(endpoint: String, completion: escaping (ResultT, Error) - Void) { guard let url URL(string: \(baseURL)/\(endpoint)) else { completion(.failure(NSError(domain: Invalid URL, code: 400))) return } let task session.dataTask(with: url) { data, response, error in if let error error { completion(.failure(error)) return } guard let data data else { completion(.failure(NSError(domain: No data received, code: 404))) return } do { let decoder JSONDecoder() let result try decoder.decode(T.self, from: data) completion(.success(result)) } catch { completion(.failure(error)) } } task.resume() } }3. 观察者模式实现protocol Observer { func update(data: Any) } class Subject { private var observers [Observer]() private var state: Any? func attach(observer: Observer) { observers.append(observer) } func detach(observer: Observer) { observers observers.filter { $0 ! observer } } func notify() { for observer in observers { observer.update(data: state ?? ) } } func setState(_ newState: Any) { state newState notify() } } class ConcreteObserver: Observer { let name: String init(name: String) { self.name name } func update(data: Any) { print(\(name) received update: \(data)) } }Swift 类提供了强大的面向对象编程能力通过合理使用继承、多态、内存管理等特性可以构建出灵活、可维护的应用程序架构。理解类的引用类型特性和适用场景是编写高质量 Swift 代码的关键。❤️❤️❤️本人水平有限如有纰漏欢迎各位大佬评论批评指正如果觉得这篇文对你有帮助的话也请给个点赞、收藏下吧非常感谢! 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