类型转换 #

let value: Any = "Hello"

if value is String {
    print("是字符串")
}

if value is Int {
    print("是整数")
}

class Animal {}
class Dog: Animal {}
class Cat: Animal {}

let dog = Dog()
let cat = Cat()
let animals: [Animal] = [dog, cat]

for animal in animals {
    if animal is Dog {
        print("这是一只狗")
    } else if animal is Cat {
        print("这是一只猫")
    }
}

protocol Drawable {
    func draw()
}

class Circle: Drawable {
    func draw() {
        print("画圆")
    }
}

class Square {
    func draw() {
        print("画方")
    }
}

let shapes: [Any] = [Circle(), Square()]

for shape in shapes {
    if shape is Drawable {
        print("可以绘制")
    }
}

class Animal {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class Dog: Animal {
    var breed: String
    init(name: String, breed: String) {
        self.breed = breed
        super.init(name: name)
    }
}

let dog = Dog(name: "旺财", breed: "金毛")
let animal = dog as Animal
print(animal.name)

let animals: [Animal] = [
    Dog(name: "旺财", breed: "金毛"),
    Animal(name: "动物")
]

for animal in animals {
    if let dog = animal as? Dog {
        print("狗: \(dog.name), 品种: \(dog.breed)")
    } else {
        print("普通动物: \(animal.name)")
    }
}

let animal: Animal = Dog(name: "旺财", breed: "金毛")
let dog = animal as! Dog
print(dog.breed)

let anotherAnimal = Animal(name: "动物")
let anotherDog = anotherAnimal as! Dog

let swiftString = "Hello"
let nsString = swiftString as NSString

let swiftArray = [1, 2, 3]
let nsArray = swiftArray as NSArray

var anyValue: Any = 42
anyValue = "Hello"
anyValue = [1, 2, 3]
anyValue = { print("闭包") }

class Person {
    var name: String
    init(name: String) {
        self.name = name
    }
}

var anyObject: AnyObject = Person(name: "张三")
anyObject = UIView()

let mixedArray: [Any] = [
    42,
    "Hello",
    3.14,
    [1, 2, 3],
    Person(name: "张三")
]

for item in mixedArray {
    switch item {
    case let intValue as Int:
        print("整数: \(intValue)")
    case let stringValue as String:
        print("字符串: \(stringValue)")
    case let doubleValue as Double:
        print("浮点数: \(doubleValue)")
    case let array as [Int]:
        print("数组: \(array)")
    case let person as Person:
        print("人: \(person.name)")
    default:
        print("未知类型")
    }
}

let value: Any = 42

switch value {
case is Int:
    print("是整数")
case is String:
    print("是字符串")
case is Double:
    print("是浮点数")
default:
    print("未知类型")
}

let value: Any = "Hello"

switch value {
case let intValue as Int:
    print("整数: \(intValue)")
case let stringValue as String:
    print("字符串: \(stringValue)")
case let doubleValue as Double:
    print("浮点数: \(doubleValue)")
default:
    print("未知类型")
}

let optionalValue: Any = Optional(42)

switch optionalValue {
case let wrapped?:
    print("有值: \(wrapped)")
case nil:
    print("无值")
}

typealias Age = Int
typealias Name = String
typealias Coordinate = (x: Double, y: Double)

var age: Age = 25
var name: Name = "张三"
var point: Coordinate = (x: 10.0, y: 20.0)

typealias Completion = () -> Void
typealias Result<T> = (T?, Error?) -> Void
typealias Transform<T, U> = (T) -> U

var callback: Completion = {
    print("完成")
}

var handler: Result<String> = { result, error in
    if let result = result {
        print(result)
    }
}

typealias DataSource = UITableViewDataSource & UICollectionViewDataSource
typealias Delegate = UITableViewDelegate & UICollectionViewDelegate

class ViewController: UIViewController {
    var dataSource: DataSource?
    var delegate: Delegate?
}

let json: [String: Any] = [
    "name": "张三",
    "age": 25,
    "scores": [90, 85, 88]
]

if let name = json["name"] as? String,
   let age = json["age"] as? Int,
   let scores = json["scores"] as? [Int] {
    print("姓名: \(name)")
    print("年龄: \(age)")
    print("成绩: \(scores)")
}

func handleViewController(_ vc: UIViewController) {
    if let navVC = vc as? UINavigationController {
        print("导航控制器")
    } else if let tabVC = vc as? UITabBarController {
        print("标签控制器")
    } else {
        print("普通控制器")
    }
}

let numbers = [1, 2, 3, 4, 5]
let anyArray: [Any] = numbers.map { $0 as Any }

let strings = ["1", "2", "3"]
let ints = strings.compactMap { Int($0) }
print(ints)

let integer = 42
let double = 3.14
let string = "Hello"
let array = [1, 2, 3]
let dictionary = ["key": "value"]

print(type(of: integer))
print(type(of: double))
print(type(of: string))

let numbers: [Double] = [1, 2, 3]
let doubled = numbers.map { $0 * 2 }
print(type(of: doubled))

func acceptString(_ value: String) { }
acceptString("Hello")

let explicitInt: Int = 42
let explicitDouble: Double = 3
let explicitArray: [String] = ["a", "b", "c"]

var name: String = "Swift"
name = 42

var age: Int = 25
age = "25"

func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}

let result = add(1, 2.0)

var name: String? = "Swift"
let length = name.count
let safeLength = name?.count ?? 0