swift 获取字符串的高度和宽度

extension String {

    ///根据宽度跟字体，计算文字的高度

    func textAutoHeight(width:CGFloat, font:UIFont) ->CGFloat{

        let string =self as NSString

        let origin = NSStringDrawingOptions.usesLineFragmentOrigin

        let lead = NSStringDrawingOptions.usesFontLeading

        let ssss = NSStringDrawingOptions.usesDeviceMetrics

        let rect = string.boundingRect(with:CGSize(width: width, height:0), options: [origin,lead,ssss], attributes: [NSAttributedString.Key.font:font], context:nil)

        return rect.height

    }

    ///根据高度跟字体，计算文字的宽度

    func textAutoWidth(height:CGFloat, font:UIFont) ->CGFloat{

        let string =self as NSString

        let origin = NSStringDrawingOptions.usesLineFragmentOrigin

        let lead = NSStringDrawingOptions.usesFontLeading

        let rect = string.boundingRect(with:CGSize(width:0, height: height), options: [origin,lead], attributes: [NSAttributedString.Key.font:font], context:nil)

        return rect.width

    }

}