方法 #

class Counter {
    var count = 0
    
    func increment() {
        count += 1
    }
    
    func increment(by amount: Int) {
        count += amount
    }
    
    func reset() {
        count = 0
    }
}

let counter = Counter()
counter.increment()
counter.increment(by: 5)
print(counter.count)

struct Point {
    var x: Double
    var y: Double
    
    func distance(to point: Point) -> Double {
        let dx = x - point.x
        let dy = y - point.y
        return sqrt(dx * dx + dy * dy)
    }
    
    mutating func moveBy(x deltaX: Double, y deltaY: Double) {
        self = Point(x: x + deltaX, y: y + deltaY)
    }
}

struct Point {
    var x: Double
    var y: Double
    
    mutating func moveBy(x deltaX: Double, y deltaY: Double) {
        x += deltaX
        y += deltaY
    }
}

var point = Point(x: 0, y: 0)
point.moveBy(x: 10, y: 20)
print("(\(point.x), \(point.y))")

struct MathUtility {
    static func square(_ x: Double) -> Double {
        return x * x
    }
    
    static func cube(_ x: Double) -> Double {
        return x * x * x
    }
}

print(MathUtility.square(5))
print(MathUtility.cube(3))

class Animal {
    class func description() -> String {
        return "这是一个动物"
    }
    
    static func count() -> Int {
        return 0
    }
}

class Dog: Animal {
    override class func description() -> String {
        return "这是一只狗"
    }
}

print(Animal.description())
print(Dog.description())

class Product {
    var name: String
    var price: Double
    
    init(name: String, price: Double) {
        self.name = name
        self.price = price
    }
    
    static func createDefault() -> Product {
        return Product(name: "默认产品", price: 0)
    }
    
    static func createPremium() -> Product {
        return Product(name: "高级产品", price: 100)
    }
}

let defaultProduct = Product.createDefault()
let premiumProduct = Product.createPremium()

struct TimesTable {
    let multiplier: Int
    
    subscript(index: Int) -> Int {
        return multiplier * index
    }
}

let timesTable = TimesTable(multiplier: 3)
print(timesTable[5])

struct Matrix {
    var rows: Int
    var columns: Int
    private var grid: [Double]
    
    init(rows: Int, columns: Int) {
        self.rows = rows
        self.columns = columns
        grid = Array(repeating: 0, count: rows * columns)
    }
    
    subscript(row: Int, column: Int) -> Double {
        get {
            return grid[row * columns + column]
        }
        set {
            grid[row * columns + column] = newValue
        }
    }
}

var matrix = Matrix(rows: 2, columns: 2)
matrix[0, 0] = 1.0
matrix[0, 1] = 2.0
matrix[1, 0] = 3.0
matrix[1, 1] = 4.0

print(matrix[0, 0])
print(matrix[1, 1])

enum Direction: Int {
    case north = 0
    case south
    case east
    case west
    
    static subscript(direction: String) -> Direction? {
        switch direction.lowercased() {
        case "north": return .north
        case "south": return .south
        case "east": return .east
        case "west": return .west
        default: return nil
        }
    }
}

if let direction = Direction["north"] {
    print(direction)
}

class Calculator {
    func add(_ a: Int, _ b: Int = 0) -> Int {
        return a + b
    }
    
    func multiply(_ a: Int, by b: Int = 1) -> Int {
        return a * b
    }
}

let calc = Calculator()
print(calc.add(5))
print(calc.add(5, 3))

class Math {
    func sum(_ numbers: Int...) -> Int {
        return numbers.reduce(0, +)
    }
    
    func average(_ numbers: Double...) -> Double {
        guard !numbers.isEmpty else { return 0 }
        return numbers.reduce(0, +) / Double(numbers.count)
    }
}

let math = Math()
print(math.sum(1, 2, 3, 4, 5))
print(math.average(1.0, 2.0, 3.0, 4.0, 5.0))

func swap(_ a: inout Int, _ b: inout Int) {
    let temp = a
    a = b
    b = temp
}

var x = 1
var y = 2
swap(&x, &y)
print("x: \(x), y: \(y)")

class Builder {
    private var name: String = ""
    private var age: Int = 0
    
    func setName(_ name: String) -> Builder {
        self.name = name
        return self
    }
    
    func setAge(_ age: Int) -> Builder {
        self.age = age
        return self
    }
    
    func build() -> String {
        return "\(name), \(age)岁"
    }
}

let result = Builder()
    .setName("张三")
    .setAge(25)
    .build()
print(result)

protocol SortStrategy {
    func sort(_ numbers: [Int]) -> [Int]
}

class AscendingSort: SortStrategy {
    func sort(_ numbers: [Int]) -> [Int] {
        return numbers.sorted { $0 < $1 }
    }
}

class DescendingSort: SortStrategy {
    func sort(_ numbers: [Int]) -> [Int] {
        return numbers.sorted { $0 > $1 }
    }
}

class Sorter {
    private var strategy: SortStrategy
    
    init(strategy: SortStrategy) {
        self.strategy = strategy
    }
    
    func setStrategy(_ strategy: SortStrategy) {
        self.strategy = strategy
    }
    
    func sort(_ numbers: [Int]) -> [Int] {
        return strategy.sort(numbers)
    }
}

protocol Command {
    func execute()
    func undo()
}

class Light {
    func on() { print("灯开了") }
    func off() { print("灯关了") }
}

class LightOnCommand: Command {
    private let light: Light
    
    init(light: Light) {
        self.light = light
    }
    
    func execute() { light.on() }
    func undo() { light.off() }
}

class LightOffCommand: Command {
    private let light: Light
    
    init(light: Light) {
        self.light = light
    }
    
    func execute() { light.off() }
    func undo() { light.on() }
}

class RemoteControl {
    private var command: Command?
    
    func setCommand(_ command: Command) {
        self.command = command
    }
    
    func pressButton() {
        command?.execute()
    }
    
    func pressUndo() {
        command?.undo()
    }
}