Swiftのジェネリクスと型キャストを用いた汎用関数の設計法

func swap<T>(a: inout T, b: inout T) {
    let temp = a
    a = b
    b = temp
}

class Animal {}
class Dog: Animal {}

let myDog: Animal = Dog()

// アップキャスト
let animal: Animal = myDog

// ダウンキャスト
if let myDog = animal as? Dog {
    print("This is a dog")
} else {
    print("This is not a dog")
}

func process<T>(item: T) {
    // 処理内容
}

func findMax<T: Comparable>(in array: [T]) -> T? {
    guard !array.isEmpty else { return nil }
    var maxValue = array[0]

    for value in array {
        if value > maxValue {
            maxValue = value
        }
    }
    return maxValue
}

// 使用例
let intArray = [3, 5, 1, 4, 2]
if let maxInt = findMax(in: intArray) {
    print("最大値: \(maxInt)") // 最大値: 5
}

let doubleArray = [2.5, 3.6, 1.1, 4.0]
if let maxDouble = findMax(in: doubleArray) {
    print("最大値: \(maxDouble)") // 最大値: 4.0
}

func removeDuplicates<T: Hashable>(from array: [T]) -> [T] {
    var uniqueElements = Set<T>()
    var result: [T] = []

    for element in array {
        if uniqueElements.insert(element).inserted {
            result.append(element)
        }
    }
    return result
}

// 使用例
let arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]
let uniqueArray = removeDuplicates(from: arrayWithDuplicates)
print("ユニークな要素: \(uniqueArray)") // ユニークな要素: [1, 2, 3, 4, 5]

class Animal {
    func makeSound() {
        print("Animal sound")
    }
}

class Dog: Animal {
    override func makeSound() {
        print("Woof!")
    }
}

class Cat: Animal {
    override func makeSound() {
        print("Meow!")
    }
}

func describeAnimal(animal: Animal) {
    if let dog = animal as? Dog {
        print("これは犬です。")
        dog.makeSound()
    } else if let cat = animal as? Cat {
        print("これは猫です。")
        cat.makeSound()
    } else {
        print("これは未知の動物です。")
        animal.makeSound()
    }
}

// 使用例
let myDog = Dog()
let myCat = Cat()

describeAnimal(animal: myDog) // これは犬です。Woof!
describeAnimal(animal: myCat) // これは猫です。Meow!

func calculateArea(of shape: Any) {
    if let circle = shape as? (radius: Double) {
        let area = Double.pi * circle.radius * circle.radius
        print("円の面積: \(area)")
    } else if let rectangle = shape as? (width: Double, height: Double) {
        let area = rectangle.width * rectangle.height
        print("長方形の面積: \(area)")
    } else {
        print("不明な形状です。")
    }
}

// 使用例
calculateArea(of: (radius: 5.0)) // 円の面積: 78.53981633974483
calculateArea(of: (width: 4.0, height: 5.0)) // 長方形の面積: 20.0

func processArray<T>(array: [T]) {
    for element in array {
        if let number = element as? Int {
            print("整数: \(number), その二倍: \(number * 2)")
        } else if let text = element as? String {
            print("文字列: \(text), 文字列の長さ: \(text.count)")
        } else {
            print("未知の型: \(element)")
        }
    }
}

// 使用例
let mixedArray: [Any] = [1, "Hello", 3, "World", 5]
processArray(array: mixedArray)
// 整数: 1, その二倍: 2
// 文字列: Hello, 文字列の長さ: 5
// 整数: 3, その二倍: 6
// 文字列: World, 文字列の長さ: 5
// 整数: 5, その二倍: 10

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

class Product {
    var title: String
    init(title: String) {
        self.title = title
    }
}

func extractTitles<T>(from array: [T]) -> [String] {
    var titles: [String] = []

    for item in array {
        if let person = item as? Person {
            titles.append(person.name)
        } else if let product = item as? Product {
            titles.append(product.title)
        }
    }

    return titles
}

// 使用例
let items: [Any] = [Person(name: "Alice"), Product(title: "Laptop"), Person(name: "Bob")]
let titles = extractTitles(from: items)
print(titles) // ["Alice", "Laptop", "Bob"]

func processShape(shape: Any) {
    if let circle = shape as? (radius: Double) {
        let area = Double.pi * circle.radius * circle.radius
        print("円の面積: \(area)")
    } else if let rectangle = shape as? (width: Double, height: Double) {
        let area = rectangle.width * rectangle.height
        print("長方形の面積: \(area)")
    } else {
        print("不明な形状です。")
    }
}

enum ShapeError: Error {
    case invalidShape
}

func calculateArea(of shape: Any) throws -> Double {
    if let circle = shape as? (radius: Double) {
        return Double.pi * circle.radius * circle.radius
    } else if let rectangle = shape as? (width: Double, height: Double) {
        return rectangle.width * rectangle.height
    } else {
        throw ShapeError.invalidShape
    }
}

// 使用例
do {
    let area = try calculateArea(of: (radius: 5.0))
    print("面積: \(area)")
} catch ShapeError.invalidShape {
    print("エラー: 不明な形状です。")
}

func safeProcessArray<T>(array: [T]) {
    for element in array {
        if let number = element as? Int {
            print("整数: \(number), その二倍: \(number * 2)")
        } else if let text = element as? String {
            print("文字列: \(text), 文字列の長さ: \(text.count)")
        } else {
            print("未知の型: \(element), デフォルト値を使用します。")
            print("デフォルトの整数: 0")
        }
    }
}

// 使用例
safeProcessArray(array: ["Hello", 42, 3.14])

func filterArray<T>(array: [T], condition: (T) -> Bool) -> [T] {
    var result: [T] = []
    for item in array {
        if condition(item) {
            result.append(item)
        }
    }
    return result
}

// 使用例
let numbers = [1, 2, 3, 4, 5, 6]
let evenNumbers = filterArray(array: numbers) { $0 % 2 == 0 }
print("偶数: \(evenNumbers)") // 偶数: [2, 4, 6]

let names = ["Alice", "Bob", "Charlie"]
let longNames = filterArray(array: names) { $0.count > 3 }
print("長い名前: \(longNames)") // 長い名前: ["Alice", "Charlie"]

func convertToString<T>(value: T) -> String {
    if let intValue = value as? Int {
        return "整数: \(intValue)"
    } else if let doubleValue = value as? Double {
        return "倍精度浮動小数点数: \(doubleValue)"
    } else if let stringValue = value as? String {
        return "文字列: \(stringValue)"
    } else {
        return "未知の型"
    }
}

// 使用例
print(convertToString(value: 42))       // 整数: 42
print(convertToString(value: 3.14))     // 倍精度浮動小数点数: 3.14
print(convertToString(value: "Swift"))   // 文字列: Swift
print(convertToString(value: true))      // 未知の型

class User {
    var name: String
    var age: Int
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
}

func displayUserInfo<T>(users: [T]) {
    for user in users {
        if let userInfo = user as? User {
            print("名前: \(userInfo.name), 年齢: \(userInfo.age)")
        }
    }
}

// 使用例
let usersArray: [Any] = [User(name: "Alice", age: 30), User(name: "Bob", age: 25)]
displayUserInfo(users: usersArray)
// 名前: Alice, 年齢: 30
// 名前: Bob, 年齢: 25

class Book {
    var title: String
    var author: String

    init(title: String, author: String) {
        self.title = title
        self.author = author
    }
}

class Movie {
    var title: String
    var director: String

    init(title: String, director: String) {
        self.title = title
        self.director = director
    }
}

class Book {
    var title: String
    var author: String

    init(title: String, author: String) {
        self.title = title
        self.author = author
    }
}

class Movie {
    var title: String
    var director: String

    init(title: String, director: String) {
        self.title = title
        self.director = director
    }
}