دوال التمديد (Extensions)

extension Int {
    func squared() -> Int {
        return self * self
    }
    var isEven: Bool {
        return self % 2 == 0
    }
}

print(4.squared())   // 16
print(5.isEven)      // false

extension String {
    func shout() -> String {
        return self.uppercased() + "!"
    }
}
print("hi".shout())   // HI!

struct Point { var x: Int; var y: Int }

extension Point {
    func distanceFromOrigin() -> Double {
        return Double(x * x + y * y).squareRoot()
    }
}