获取文本内容高度和宽度

extension NSString {

    func stringWidthFont(viewLab: UILabel) -> CGSize {

        if self.length < 1 {
            return CGSizeMake(10, 10)
        }

        let size = self.boundingRectWithSize(CGSizeMake(viewLab.frame.width, CGFloat.max), options: .UsesLineFragmentOrigin, attributes: [NSFontAttributeName: viewLab.font], context: nil)

        return size.size
    }
}