设置uitextview的行间距

let paragraphStyle: NSMutableParagraphStyle = NSMutableParagraphStyle()
paragraphStyle.lineSpacing = 20
// 字体的行间距
let attributes: [String : AnyObject] = [NSFontAttributeName: UIFont.systemFontOfSize(15), NSParagraphStyleAttributeName: paragraphStyle]
contentView.attributedText = NSAttributedString(string: contentView.text!, attributes: attributes)