イニシャライザ

/* イニシャライザ */
struct Color {
    // let red = 0.0, green = 0.0, blue = 0.0 // error: immutable value 'self.red' may only be initialized once
    let red, green, blue : Double
    init(red: Double, green: Double, blue: Double) {
        self.red   = red
        self.green = green
        self.blue  = blue
    }
}
 
let magenta = Color(red: 1.0, green: 0.0, blue: 1.0)