如何使用UIColor值创建Swift枚举？

Question

我正在制作一个绘图应用程序,我想通过使用枚举来引用我的颜色.例如,Colors.RedColor每次我想要那种红色时,使用它会更干净,更方便,而不是输入值.但是,Swift的原始值枚举似乎不接受UIColor作为一种类型.有没有办法用枚举或类似的方法做到这一点？

Answer 1

我这样做(基本上使用结构作为命名空间):

extension UIColor {
  struct MyTheme {
    static var firstColor: UIColor  { return UIColor(red: 1, green: 0, blue: 0, alpha: 1) }
    static var secondColor: UIColor { return UIColor(red: 0, green: 1, blue: 0, alpha: 1) }
  }
}

你使用它像:

UIColor.MyTheme.firstColor

因此,您可以在自定义主题中使用红色.

Answer 2

如果您的颜色不是UIColor便利方法定义的颜色之一,您可以添加扩展名UIColor:

extension UIColor {
    static var firstColor: UIColor  { return UIColor(red: 1, green: 0, blue: 0, alpha: 1) }
    static var secondColor: UIColor { return UIColor(red: 0, green: 1, blue: 0, alpha: 1) }
}

// Usage
let myColor = UIColor.firstColor

Answer 3

我使用计算属性来解决这个问题,这是我的代码

enum MyColor {
    case navigationBarBackgroundColor
    case navigationTintCololr
}

extension MyColor {
    var value: UIColor {
        get {
            switch self {
            case .navigationBarBackgroundColor:
                return UIColor(red: 67/255, green: 173/255, blue: 247/255, alpha: 1.0)
            case .navigationTintCololr:
                return UIColor.white
            }
        }
    }
}

然后我可以像这样使用MyColor:

MyColor.navigationBarBackgroundColor.value

Answer 4

如何使用UIColor值创建Swift枚举？

这实际上就是使用UIColor值创建枚举的方式：

import UIKit

final class Color: UIColor, RawRepresentable, ExpressibleByStringLiteral
{
    // MARK:- ExpressibleByStringLiteral

    typealias StringLiteralType = String

    convenience init(stringLiteral: String) {
        guard let (a,r,g,b) = Color.argb(hexColor: stringLiteral) else {
            assertionFailure("Invalid string")
            self.init(red: 0, green: 0, blue: 0, alpha: 0)
            return
        }
        self.init(red: r, green: g, blue: b, alpha: a)
    }

    // MARK:- RawRepresentable

    public typealias RawValue = String

    convenience init?(rawValue: RawValue) {
        guard let (a,r,g,b) = Color.argb(hexColor: rawValue) else { return nil }
        self.init(red: r, green: g, blue: b, alpha: a)
    }

    var rawValue: RawValue {
        return hexString()
    }

    // MARK:- Private

    /// Return color components in range [0,1] for hexadecimal color strings.
    /// - hexColor: case-insensitive string with format RGB, RRGGBB, or AARRGGBB.
    private static func argb(hexColor: String) -> (CGFloat,CGFloat,CGFloat,CGFloat)?
    {
        let hexAlphabet = "0123456789abcdefABCDEF"
        let hex = hexColor.trimmingCharacters(in: CharacterSet(charactersIn: hexAlphabet).inverted)
        var int = UInt32()
        Scanner(string: hex).scanHexInt32(&int)
        let a, r, g, b: UInt32
        switch hex.count {
        case 3: (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17) // RGB
        case 6: (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF) // RRGGBB
        case 8: (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF) // AARRGGBB
        default: return nil
        }
        return (CGFloat(a)/255, CGFloat(r)/255, CGFloat(g)/255, CGFloat(b)/255)
    }

    private func hexString() -> String {
        var red:   CGFloat = 0
        var green: CGFloat = 0
        var blue:  CGFloat = 0
        var alpha: CGFloat = 0
        if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
            return String(format: "#%02X%02X%02X%02X", UInt8(red * 255), UInt8(green * 255), UInt8(blue * 255), UInt8(alpha * 255))
        }
        assertionFailure("Invalid colour space.")
        return "#F00"
    }
}

enum Colors: Color {
    case red = "#F00"
//    case blue = "#F00" // Raw value for enum case is not unique
}

let color3 = Color(rawValue: "#000") // RGB
let color6 = Color(rawValue: "#123456") // RRGGBB
let color8 = Color(rawValue: "#12345678") // AARRGGBB
print(Colors(rawValue:"#F00") as Any) // red
print(Colors(rawValue:"#FF0000") as Any) // red
print(Colors(rawValue:"#FFFF0000") as Any) // red
print(Colors(rawValue:"#ABC") as Any) // nil because it’s not a member of the enumeration
// print(Colors(rawValue:"#XYZ") as Any) // assertion on debug, black on release
print(Colors.red) // red
print(Colors.red.rawValue) // UIExtendedSRGBColorSpace 1 0 0 1

在...的帮助下

• benhurott / UIColorExtension.md
• Swift 3 UIColor实用程序，可从十六进制代码获得随机颜色和颜色
• 原始类型“布尔”不能用任何文字表示