Swift - Enum的相关值或扩展名

Question

关于swift枚举的一般问题.

我想创建一个"icon"的枚举,并将一个值"关联"到枚举的情况

enum Icon {
  case plane
  case arrow
  case logo
  case flag
}

我想为枚举值创建一个关联的图像.还有枚举值的相关颜色

因此,例如,如果有可能做类似的事情:

extension Icon.plane {
  var image = {
    get {
       return UIImage("plane.png")
    }
  }
  var color = {
    get {
       return UIColor.greenColor()
    }
  }
}


var image = Icon.arrow.image // the image associated to the enum
var color = Icon.arrow.color // the color associated to the enum

这类事可能吗？

Answer 1

遗憾的是,您无法根据枚举情况定义静态属性,但您可以使用计算属性并switch为每种情况返回值:

enum Icon {
    case plane
    case arrow
    case logo
    case flag

    var image: UIImage {
        switch self {
            case .plane: return UIImage(named: "plane.png")!
            case .arrow: return UIImage(named: "arrow.png")!
            case .logo: return UIImage(named: "logo.png")!
            case .flag: return UIImage(named: "flag.png")!
        }
    }

    var color: UIColor {
        switch self {
        case .plane: return UIColor.greenColor()
        case .arrow: return UIColor.greenColor()
        case .logo: return UIColor.greenColor()
        case .flag: return UIColor.greenColor()
        }
    }
}

// usage
Icon.plane.color

Answer 2

使用具有关联值的枚举结合switch语句,您可以非常灵活.第一个例子:

enum Icon {
    case plane(img:UIImage, col:UIColor)
    case arrow(img:UIImage, col:UIColor)
    case logo(img:UIImage, col:UIColor)
    case flag(img:UIImage, col:UIColor)

    var values:(img:UIImage,col:UIColor) {
        switch self {
        case let .plane(image, color):
            return (image,color)
        case let .arrow(image, color):
            return (image,color)
        case let .logo(image, color):
            return (image,color)
        case let .flag(image, color):
            return (image,color)
        }
    }
}



var a = Icon.plane(img: UIImage(named: "image.png")!, col: UIColor.blueColor())

a.values.col
a.values.img

和第二个例子:

enum Icon {
    case plane(img:UIImage, col:UIColor)
    case arrow(img:UIImage, col:UIColor)
    case logo(img:UIImage, col:UIColor)
    case flag(img:UIImage, col:UIColor)

    var img:UIImage {
        switch self {
        case let .plane(image, color):
            return image
        case let .arrow(image, color):
            return image
        case let .logo(image, color):
            return image
        case let .flag(image, color):
            return image
        }
    }

    var col:UIColor {
        switch self {
        case let .plane(image, color):
            return color
        case let .arrow(image, color):
            return color
        case let .logo(image, color):
            return color
        case let .flag(image, color):
            return color
        }
    }
}



var a = Icon.plane(img: UIImage(named: "image.png")!, col: UIColor.blueColor())

a.col
a.img

不需要扩展.如果你真的想要静态值,你可以这样做:

struct MyIcon {
    static let plane = Icon.plane(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
    static let arrow = Icon.arrow(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
    static let logo = Icon.logo(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
    static let flag = Icon.flag(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
}

MyIcon.arrow.col

这可能比将固定的文字值放在switch语句中更整洁.