swift 宏定义

swift中没有宏定义了，但是OC当中宏的习惯一时还改不了，想实现类似效果

xcode → File → New → File → Cocoa Touch Class → Next 

把uikit 下边的 删掉，然后就可以写了（其实是声明的全局变量）

import UIKit

let ScreenWidth = UIScreen.main.bounds.size.width
let ScreenHeight = UIScreen.main.bounds.size.height
// rgb颜色转换
func UIColorFromRGB (hex:String) -> UIColor {
    var cString:String =  hex.trimmingCharacters(in: NSCharacterSet.whitespacesAndNewlines)
    if (cString.hasPrefix("#")) {
        cString = (cString as NSString).substring(from: 1)
    }
    let rString = (cString as NSString).substring(to: 2)
    let gString = ((cString as NSString).substring(from: 2) as NSString).substring(to: 2)
    let bString = ((cString as NSString).substring(from: 4) as NSString).substring(to: 2)
    
    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))
}

编译一下，就可以使用了 ，weakself 好像没办法像OC一样宏定了 只能在用的时候，这样写

   weak var weakSelf = self
        var view = UIView.init(frame: CGRect(x:0,y:0,width:ScreenWidth,height:ScreenHeight))

        self.view.backgroundColor=UIColorFromRGB(hex: "0Xe0e6ea")

 参考链接：   http://www.imooc.com/qadetail/68779