How can I make a Swift enum with UIColor value?

Question

I\'m making a drawing app and I would like to refer to my colors through use of an enum. For example, it would be cleaner and more convenient to use Colors.RedColor

Answer 1

This answer is probably late, but for others finding this question. I was not satisfied with the answers above, since adding colors as UIColors extension is not always what you want, since:

1. It might not be the best solution from Software architecture perspective.
2. You can not use the power enums have, e.g. CaseIterable

This is the solution I came up with:

enum PencilColor {
    case lightRed
    case darkPurple
    
    var associatedColor: UIColor {
        switch self {
        case .lightRed: return UIColor(red: 67/255, green: 173/255, blue: 247/255, alpha: 1.0)
        case .darkPurple: return UIColor(red: 67/255, green: 173/255, blue: 247/255, alpha: 1.0)
        }
    }
}

Answer 2

I use computed properties to solve this problem, this is my code

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
            }
        }
    }
}

then I can use MyColor like this:

MyColor.navigationBarBackgroundColor.value

Answer 3

I do it like this (basically using a struct as a namespace):

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) }
  }
}

And you use it like:

UIColor.MyTheme.firstColor

So you can have a red color inside your custom theme.

Answer 4

Based on @Jano's answer I made an improvement by using Int as the literal type:

import UIKit

public final class Colors: UIColor {

}

extension Colors: ExpressibleByIntegerLiteral {
    public typealias IntegerLiteralType = Int

    public convenience init(integerLiteral value: Int) {
        let red = CGFloat((value & 0xFF0000FF) >> 24) / 0xFF
        let green = CGFloat((value & 0x00FF00FF) >> 16) / 0xFF
        let blue = CGFloat((value & 0x0000FFFF) >> 8) / 0xFF
        let alpha = CGFloat(value & 0x00FF00FF) / 0xFF

        self.init(red: red, green: green, blue: blue, alpha: alpha)
    }
}

extension Colors: RawRepresentable {
    public typealias RawValue = Int

    public var rawValue: RawValue {
        return hex
    }

    public convenience init?(rawValue: RawValue) {
        self.init(integerLiteral: rawValue)
    }
}

fileprivate extension UIColor {
    var hex: Int {
        var fRed: CGFloat = 0
        var fGreen: CGFloat = 0
        var fBlue: CGFloat = 0
        var fAlpha: CGFloat = 0
        if self.getRed(&fRed, green: &fGreen, blue: &fBlue, alpha: &fAlpha) {
            let red = Int(fRed * 255.0)
            let green = Int(fGreen * 255.0)
            let blue = Int(fBlue * 255.0)
            let alpha = Int(fAlpha * 255.0)
            let rgb = (alpha << 24) + (red << 16) + (green << 8) + blue
            return rgb
        } else {
            return 0x000000
        }
    }
}

public enum MainPalette: Colors {
    case red = 0xFF0000ff
    case white = 0xFFFFFFFF
}

public enum FeatureXPalette: Colors {
    case blue = 0x024F9Eff
//    case bluish = 0x024F9Eff // <- Can't do
    case red = 0xFF0000ff
}

The advantage is that it doesn't allow duplicate colors (as a true enum) and also I support alpha.

As you can see, you can create multiple enums for different palettes/schemes. In the case you want views to be able to use any palette, you can just add a protocol:

protocol Color {
    var color: UIColor { get }
}

extension MainPalette: Color {
    var color: UIColor {
        return rawValue
    }
}

extension FeatureXPalette: Color {
    var color: UIColor {
        return rawValue
    }
}

so that way you can have a function that takes in the protocol:

func printColorEquality(color1: Color, color2: Color) {
    print(color1.color == color2.color)
}

let red1: Color = MainPalette.red
let red2: Color = FeatureXPalette.red

printColorEquality(color1: red1, color2: red2)

What I also like to do is add static vars for convenience:

extension MainPalette {
    public static var brightRed: UIColor {
        return MainPalette.red.color
    }
}

that gives you a cleaner api:

view.backgroundColor = MainPalette.brightRed

Naming can be improved: you have to choose if you want a nice convenience api or nice naming for your enums.

Answer 5

How can I make a Swift enum with UIColor value?

This is how you would literally make an enum with a UIColor value:

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

With help from

• benhurott/UIColorExtension.md
• Swift 3 UIColor utilities for random color and color from hex code
• Raw type 'Bool' is not expressible by any literal

Answer 6

Actually I use such implementation, it is very convenience for me because of two reason, first one I can use dex value and another all colors in constant

import UIKit

struct ColorPalette {
struct Gray {
    static let Light = UIColor(netHex: 0x595959)
    static let Medium = UIColor(netHex: 0x262626)
}
}

extension UIColor {
convenience init(red: Int, green: Int, blue: Int) {
    assert(red >= 0 && red <= 255, "Invalid red component")
    assert(green >= 0 && green <= 255, "Invalid green component")
    assert(blue >= 0 && blue <= 255, "Invalid blue component")

    self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
}

convenience init(netHex: Int) {
    self.init(red: (netHex >> 16) & 0xff, green: (netHex >> 8) & 0xff, blue: netHex & 0xff)
}
}

usage

let backgroundGreyColor = ColorPalette.Gray.Medium.cgColor