17.Swift学习之类

class 类名  {
    // 定义属性和方法
}

  class VideoMode {
      var resolution = Resolution()
      var interlaced = false
      var frameRate = 0.0
      var name: String?
  }

let someVideoMode = VideoMode()

print("The width of someResolution is \(someVideoMode.interlaced)")

print("The width of someVideoMode is \(someVideoMode.resolution.width)")

someVideoMode.resolution.width = 1280
print("The width of someVideoMode is now \(someVideoMode.resolution.width)")

//定义一个VideoMode类的对象
let tenEighty = VideoMode()
tenEighty.resolution = hd
tenEighty.interlaced = true
tenEighty.name = "1080i"
tenEighty.frameRate = 25.0

//定义一个常量等于上面的类的对象
let alsoTenEighty = tenEighty
alsoTenEighty.frameRate = 30.0

//同时改变
print("The frameRate property of tenEighty is now \(tenEighty.frameRate)")

if tenEighty === alsoTenEighty {
    print("tenEighty and alsoTenEighty refer to the same VideoMode instance.")
}

class Vehicle {
    var currentSpeed = 0.0
    var description: String {
        return "traveling at \(currentSpeed) miles per hour"
    }
    func makeNoise() {
       
    }
}

class Bicycle: Vehicle {
    var hasBasket = false
}

class Train: Vehicle {
    override func makeNoise() {
        print("Choo Choo")
    }
}