swift 计算文本高度

```

import UIKit

extension String{

//MARK:获得string内容高度

func stringHeightWith(fontSize:CGFloat,width:CGFloat,lineSpace : CGFloat)->CGFloat{

let font = UIFont.systemFont(ofSize: fontSize)

//        let size = CGSizeMake(width,CGFloat.max)

let size = CGSize(width: width, height: CGFloat(MAXFLOAT))

let paragraphStyle = NSMutableParagraphStyle()

paragraphStyle.lineSpacing = lineSpace

paragraphStyle.lineBreakMode = .byWordWrapping;

let attributes = [NSFontAttributeName:font, NSParagraphStyleAttributeName:paragraphStyle.copy()]

let text = self as NSString

let rect = text.boundingRect(with: size, options:.usesLineFragmentOrigin, attributes: attributes, context:nil)

return rect.size.height

}//funcstringHeightWith

}//extension end

```