Swift-枚举的关联值或扩展名 [英] Swift - Associated value or extension for an Enum

问题描述

有关快速枚举的一般问题.

General question regarding swift enum.

我想创建一个"icon"枚举并将一个值关联"到该枚举大小写

I want to create an enum of "icon" and "associate" a value to the enum case

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

我想创建一个与枚举值相关的图像. 以及与枚举值相关的颜色

I want to create an associated image to the enum's value. And also an associated color to the enum value

例如，如果有可能做类似的事情:

So for instance if it was possible to do something like:

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

这种事情有可能吗?

推荐答案

不幸的是，您无法基于枚举案例定义静态属性，但是可以使用计算属性和switch来返回每种案例的值:

Unfortunately you cannot define static properties based on enum cases, but you can use computed properties and switch to return values for each case:

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

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