Protocols trong Swift

protocol Drawable {
    func draw()
}
 
struct Circle: Drawable {
    func draw() {
        print("Drawing circle")
    }
}
 
struct Square: Drawable {
    func draw() {
        print("Drawing square")
    }
}

protocol Named {
    var name: String { get }
    var fullName: String { get set }
}
 
struct Person: Named {
    var name: String
    var fullName: String
}

protocol Togglable {
    mutating func toggle()
}
 
struct Switch: Togglable {
    var isOn = false
    
    mutating func toggle() {
        isOn.toggle()
    }
}

protocol Initializable {
    init(value: Int)
}
 
class MyClass: Initializable {
    var value: Int
    
    required init(value: Int) {
        self.value = value
    }
}

protocol Animal {
    var name: String { get }
}
 
protocol Pet: Animal {
    var owner: String { get }
}
 
struct Dog: Pet {
    var name: String
    var owner: String
}

protocol Greetable {
    var name: String { get }
    func greet()
}
 
extension Greetable {
    func greet() {
        print("Hello, \(name)!")
    }
}
 
struct Person: Greetable {
    var name: String
    // greet() có implementation mặc định
}

func render(_ drawable: Drawable) {
    drawable.draw()
}
 
let shapes: [Drawable] = [Circle(), Square()]
shapes.forEach { $0.draw() }

protocol Named { var name: String { get } }
protocol Aged { var age: Int { get } }
 
func celebrate(_ person: Named & Aged) {
    print("Happy \(person.age)th birthday, \(person.name)!")
}
 
struct Person: Named, Aged {
    var name: String
    var age: Int
}

// Equatable
struct Point: Equatable {
    var x: Int
    var y: Int
}
Point(x: 1, y: 2) == Point(x: 1, y: 2)  // true
 
// Hashable
struct Person: Hashable {
    var name: String
}
 
// Codable
struct User: Codable {
    var id: Int
    var name: String
}
 
// CustomStringConvertible
struct Item: CustomStringConvertible {
    var description: String { "Item" }
}