iOS 创建一个UIButton
示例
UIButton可以在框架中初始化：
迅速
let button = UIButton(frame: CGRect(x: x, y: y, width: width, height: height)
目标C
UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(x, y, width, height)];
可以这样创建特定类型的UIButton：
迅速
let button = UIButton(type: .Custom)
目标C
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
这里type是一个UIButtonType：
enum UIButtonType : Int {
case Custom
case System
case DetailDisclosure
case InfoLight
case InfoDark
case ContactAdd
static var RoundedRect: UIButtonType { get }
}