废话不说 直接上代码

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

    {
        let font = UIFont.systemFontOfSize(fontSize)
        let size = CGSizeMake(width,CGFloat.max)
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineBreakMode = .ByWordWrapping;
        let  attributes = [NSFontAttributeName:font,NSParagraphStyleAttributeName:paragraphStyle.copy()]
        
        let text = self as NSString
        let rect = text.boundingRectWithSize(size,options:.UsesLineFragmentOrigin,attributes: attributes,context:nil)
        return rect.size.height
    }