UIButton 是开发中高频使用的控件，一个好的封装能大大提高代码的整洁度

1. Target封装

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2. 协议封装

• 创建点击协议

@objc protocol BookHeaderViewDelegate: NSObjectProtocol {
    
    optional func headerViewDidClick(index: Int)
}

• 封装Button

private func buildButtonWithCustom(title: String, frame: CGRect, action: Selector!, tag: NSInteger) {
        let button = UIButton(type: .Custom)
        button.layer.cornerRadius = 3
        button.layer.masksToBounds = true
        button.setTitle(title, forState: .Normal)
        button.setTitleColor(UIColor.whiteColor(), forState: .Normal)
        button.tag = tag
        button.addTarget(self, action: action, forControlEvents: .TouchUpInside)
        button.frame = frame
        button.backgroundColor = UIColor.colorWithCustom(246, g: 36, b: 8)
        addSubview(button)
    }

• 添加点击方法

private func click(sender: UIButton) {
        delegate?.headerViewDidClick!(sender.tag)
    }

• 创建按钮

buildButtonWithCustom("菜　　谱", frame: CGRectMake(10, 10, (kScreenWith - 30) / 2.0, (kScreenWith - 30)  * 0.618 / 2.0), action: #selector(BookHeaderView.click),tag: 1)

3. 闭包封装

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