前面的文章里面有关于自定义验证码视图OC相关的代码，在swift_3中，大体上的结构都是相同的，只是因为swift是强类型语言，所以在局部上可能有所不同。

首先还是继承于UIButton

class VerifyCodeButton: UIButton {
}

构建视图主要是重写视图的绘制

    //重绘
    override func draw(_ rect: CGRect) 

重绘主要包括干扰线的绘制和验证码字符的绘制

干扰线的绘制

        let context = UIGraphicsGetCurrentContext()
        context!.setLineWidth(CGFloat(kLineWith));
        
        for _ in 0..<kLineCount {
            let randomCorlor = UIColor.init(colorLiteralRed: Float(arc4random()%255)/Float(255.0), green: Float(arc4random()%255)/Float(255.0), blue: Float(arc4random()%255)/Float(255.0), alpha: 1.0)
            context?.setStrokeColor(randomCorlor.cgColor)
            //起点
            pX = CGFloat(arc4random()%UInt32(rect.size.width))
            pY = CGFloat(arc4random()%UInt32(rect.size.height))
            context?.move(to: CGPoint(x: pX!, y: pY!))
            //终点
            pX = CGFloat(arc4random()%UInt32(rect.size.width))
            pY = CGFloat(arc4random()%UInt32(rect.size.height))
            context?.addLine(to: CGPoint(x: pX!, y: pY!))
            context?.strokePath();
            
        }

验证码的视图绘制

        for index in 0..<self.verifyCode.characters.count {
            pX = CGFloat(Int(arc4random()) % width) + (rect.size.width+4)/CGFloat(counts) * CGFloat(index)
            
            pY = CGFloat(arc4random()%UInt32(hight))
            point = CGPoint(x: pX!, y: pY!)
            let c = self.verifyCode[self.verifyCode.index(self.verifyCode.startIndex, offsetBy: index)]
            
            let textC :String = "\(c)"
            let randomFont = UIFont.systemFont(ofSize:CGFloat(arc4random()%5+15))
            textC.draw(at: point!, withAttributes: [NSFontAttributeName:randomFont])
        }

遇到的小坑
使用"()"构建的字符串和format构建的字符串，在characters.count上市不同的