Swift开发应用中如何更方便地使用颜色详解

import Foundation
extension UIColor {
  class func colorWithHexString(hex:String) ->UIColor {
    var cString = hex.trimmingCharacters(in:CharacterSet.whitespacesAndNewlines).uppercased()

    if (cString.hasPrefix("#")) {
      let index = cString.index(cString.startIndex, offsetBy:1)
      cString = cString.substring(from: index)
    }
    if (cString.characters.count != 6) {
      return UIColor.red
    }
    let rIndex = cString.index(cString.startIndex, offsetBy: 2)
    let rString = cString.substring(to: rIndex)
    let otherString = cString.substring(from: rIndex)
    let gIndex = otherString.index(otherString.startIndex, offsetBy: 2)
    let gString = otherString.substring(to: gIndex)
    let bIndex = cString.index(cString.endIndex, offsetBy: -2)
    let bString = cString.substring(from: bIndex)
    var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0;
    Scanner(string: rString).scanHexInt32(&r)
    Scanner(string: gString).scanHexInt32(&g)
    Scanner(string: bString).scanHexInt32(&b)
    return UIColor(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: CGFloat(1))
  }
}

import Foundation
import UIKit
struct Theme{
  static var ThemeBlue:UIColor = UIColor.colorWithHexString(hex: "#46b8ee")
  static var ThemeDarkBlue:UIColor = UIColor.colorWithHexString(hex: "#3eb5ed")
  static var ThemeDeepBlue:UIColor = UIColor.colorWithHexString(hex: "#2396cd")
  static var ThemePurple:UIColor = UIColor.colorWithHexString(hex: "#8267c6")
  static var ThemeDarkPurple:UIColor = UIColor.colorWithHexString(hex: "#7963c5")
  static var ThemeDeepPurple:UIColor = UIColor.colorWithHexString(hex: "#7059c5")
  //...
}

cell.backgroundColor = Theme.ThemeDeepPurple
cell.backgroundColor = Theme.ThemeDeepBlue