How to convert UIColor to string and string to UIColor using swift?

Question

I have an object with a UIColor property:

class Beer: NSObject {
  var color: UIColor?
  ...
}

I'm saving this to a DB, so I need to make this property into a valid JSON type, so I'm thinking of converting it to a string. How can I convert into a string to store, and then when loading using that string to create the UIColor?

Answer 1

I have put some sample for both conversion, still you can find many code for the conversion

For the conversion from UIColor to hex string you can use the following code:

extension UIColor {
    var rgbComponents:(red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
        var r:CGFloat = 0
        var g:CGFloat = 0
        var b:CGFloat = 0
        var a:CGFloat = 0
        if getRed(&r, green: &g, blue: &b, alpha: &a) {
            return (r,g,b,a)
        }
        return (0,0,0,0)
    }
    // hue, saturation, brightness and alpha components from UIColor**
    var hsbComponents:(hue: CGFloat, saturation: CGFloat, brightness: CGFloat, alpha: CGFloat) {
        var hue:CGFloat = 0
        var saturation:CGFloat = 0
        var brightness:CGFloat = 0
        var alpha:CGFloat = 0
        if getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha){
            return (hue,saturation,brightness,alpha)
        }
        return (0,0,0,0)
    }
    var htmlRGBColor:String {
        return String(format: "#%02x%02x%02x", Int(rgbComponents.red * 255), Int(rgbComponents.green * 255),Int(rgbComponents.blue * 255))
    }
    var htmlRGBaColor:String {
        return String(format: "#%02x%02x%02x%02x", Int(rgbComponents.red * 255), Int(rgbComponents.green * 255),Int(rgbComponents.blue * 255),Int(rgbComponents.alpha * 255) )
    }
}

Sample use:

let myColorBlack = UIColor.blackColor().webColor         //#000000ff
let myLghtGrayColor = UIColor.lightGrayColor().webColor  //#aaaaaaff
let myDarkGrayColor = UIColor.darkGrayColor().webColor 

For more info you can check: https://stackoverflow.com/a/28697136/4557505
https://gist.github.com/yannickl/16f0ed38f0698d9a8ae7

You can store this string inside the db and retrieve it when you need it

From HexString to UIColor

extension UIColor {
    public convenience init?(hexString: String) {
        let r, g, b, a: CGFloat

        if hexString.hasPrefix("#") {
            let start = hexString.startIndex.advancedBy(1)
            let hexColor = hexString.substringFromIndex(start)

            if hexColor.characters.count == 8 {
                let scanner = NSScanner(string: hexColor)
                var hexNumber: UInt64 = 0

                if scanner.scanHexLongLong(&hexNumber) {
                    r = CGFloat((hexNumber & 0xff000000) >> 24) / 255
                    g = CGFloat((hexNumber & 0x00ff0000) >> 16) / 255
                    b = CGFloat((hexNumber & 0x0000ff00) >> 8) / 255
                    a = CGFloat(hexNumber & 0x000000ff) / 255

                    self.init(red: r, green: g, blue: b, alpha: a)
                    return
                }
            }
        }

        return nil
    }
}

Usage:UIColor(hexString: "#ffe700ff")

Ref: https://www.hackingwithswift.com/example-code/uicolor/how-to-convert-a-hex-color-to-a-uicolor
https://github.com/yeahdongcn/UIColor-Hex-Swift
https://gist.github.com/arshad/de147c42d7b3063ef7bc

Answer 2

Here is an update for:

1. Swift 5.0
2. combination for UIKit-n-SwiftUI architecture
3. #RRGGBBAA / #RRGGBB color values

__

import UIKit
import SwiftUI

extension Color {

    init?(hexString: String) {

        let rgbaData = getrgbaData(hexString: hexString)

        if(rgbaData != nil){

            self.init(
                        .sRGB,
                        red:     Double(rgbaData!.r),
                        green:   Double(rgbaData!.g),
                        blue:    Double(rgbaData!.b),
                        opacity: Double(rgbaData!.a)
                    )
            return
        }
        return nil
    }
}

extension UIColor {

    public convenience init?(hexString: String) {

        let rgbaData = getrgbaData(hexString: hexString)

        if(rgbaData != nil){
            self.init(
                        red:   rgbaData!.r,
                        green: rgbaData!.g,
                        blue:  rgbaData!.b,
                        alpha: rgbaData!.a)
            return
        }
        return nil
    }
}

private func getrgbaData(hexString: String) -> (r: CGFloat, g: CGFloat, b: CGFloat, a: CGFloat)? {

    var rgbaData : (r: CGFloat, g: CGFloat, b: CGFloat, a: CGFloat)? = nil

    if hexString.hasPrefix("#") {

        let start = hexString.index(hexString.startIndex, offsetBy: 1)
        let hexColor = String(hexString[start...]) // Swift 4

        let scanner = Scanner(string: hexColor)
        var hexNumber: UInt64 = 0

        if scanner.scanHexInt64(&hexNumber) {

            rgbaData = { // start of a closure expression that returns a Vehicle
                switch hexColor.count {
                case 8:

                    return ( r: CGFloat((hexNumber & 0xff000000) >> 24) / 255,
                             g: CGFloat((hexNumber & 0x00ff0000) >> 16) / 255,
                             b: CGFloat((hexNumber & 0x0000ff00) >> 8)  / 255,
                             a: CGFloat( hexNumber & 0x000000ff)        / 255
                           )
                case 6:

                    return ( r: CGFloat((hexNumber & 0xff0000) >> 16) / 255,
                             g: CGFloat((hexNumber & 0x00ff00) >> 8)  / 255,
                             b: CGFloat((hexNumber & 0x0000ff))       / 255,
                             a: 1.0
                           )
                default:
                    return nil
                }
            }()

        }
    }

    return rgbaData
}