Swift - Associated value or extension for an Enum

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有刺的猬
有刺的猬 2021-02-01 19:43

General question regarding swift enum.

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

enum Icon {
  case plane
  case ar         


        
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4条回答
  • 2021-02-01 20:03

    More cleaner and readable

    enum Icon {
        case plane
        case arrow
        case logo
        case flag
    
        var image: UIImage {
            return value.image
        }
    
        var color: UIColor {
            return value.color
        }
    
        private var value: (image: UIImage, color: UIColor) {
            switch self {
            case .plane: return (UIImage(named: "plane.png")!, UIColor.green)
            case .arrow: return (UIImage(named: "arrow.png")!, UIColor.green)
            case .logo: return (UIImage(named: "logo.png")!, UIColor.green)
            case .flag: return (UIImage(named: "flag.png")!, UIColor.green)
            }
        }
    }
    
    // Use
    Icon.plane.image
    Icon.plane.color
    
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  • 2021-02-01 20:08

    Using enums with associated values combined with switch statements you can be very flexible. A first example:

    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
    

    and a second example:

    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
    

    no need for extensions. And if you really do want static values, you could do this:

    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
    

    which might be tidier than placing the fixed literal values inside a switch statement.

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  • 2021-02-01 20:13

    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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  • 2021-02-01 20:22

    Shorter and safer code:

    import UIKit
    
    enum Icon: String {
    
        case plane, arrow, logo, flag
    
        var image: UIImage {
    
            // If the image is not available, provide a default value so we dont force optional unwrapping
            return UIImage(named: "\(self.rawValue).png") ?? UIImage()
        }
    
        var color: UIColor {
            switch self {
            case .plane: return UIColor.green
            case .arrow: return UIColor.green
            case .logo: return UIColor.green
            case .flag: return UIColor.green
            }
        }
    }
    
    // Usage
    Icon.plane.color
    Icon.arrow.image
    
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