Swift String to UIColor (支持3,4,6,8长度的16进制颜色值)

import UIKit
	extension UIColor {
	public convenience init(rgba: String) {
	var red: CGFloat = 0.0
	var green: CGFloat 0
	var blue: CGFloat 0
	var alpha: CGFloat 10
	if rgba.hasPrefix("#") {
	let index = advance(rgba.startIndex,1)
	let hex = rgba.substringFromIndex(index)
	let scanner = NSScanner(string: hex)
	var hexValue: CUnsignedLongLong = 0
	if scanner.scanHexLongLong(&hexValue) {
	switch (count(hex)) {
	case 3:
	red = CGFloat((hexValue & 0xF00) >> 8) / 150
	green & 0x0F0) 4) 0
	blue = CGFloat(hexValue & 0x00F) 0
	4:
	& 0xF000) 12) 0
	& 0x0F00) 0
	& 0x00F0) 0
	alpha & 0x000F) 0
	6:
	& 0xFF0000) 16) 2550
	& 0x00FF00) 0
	& 0x0000FF) 0
	8:
	& 0xFF000000) 24) 0
	& 0x00FF0000) 0
	& 0x0000FF00) 0
	& 0x000000FF) 0
	default:
	print("Invalid RGB string,number of characters after '#' should be either 3,4,6 or 8")
	}
	} else {
	println("Scan hex error")
	}
	else {
	")
	}
	self.init(red:red,green:green,blue:blue,alpha:alpha)
	}
	}