swift-自动计算字符串的宽高

写一个方法来继承String

//自动控制文字换行及宽度

extension String {

func textSizeWithFont(font: UIFont, constrainedToSize size:CGSize) -> CGSize {

var textSize:CGSize!

if CGSizeEqualToSize(size, CGSizeZero) {

let attributes = NSDictionary(object: font, forKey: NSFontAttributeName)

textSize = self.sizeWithAttributes(attributes as! [String : AnyObject] as [String : AnyObject])

} else {

let option = NSStringDrawingOptions.UsesLineFragmentOrigin

let attributes = NSDictionary(object: font, forKey: NSFontAttributeName)

let stringRect = self.boundingRectWithSize(size, options: option, attributes: attributes as! [String : AnyObject] as [String : AnyObject], context: nil)

textSize = stringRect.size

}

return textSize

}

}

用法：

　　　let projectText="我是一段字符串，来计算我的高度吧";

let projectSize=projectText.textSizeWithFont(UIFont.systemFontOfSize(14), constrainedToSize:CGSizeMake(100, 200))

let comProjectW:CGFloat=projectSize.width;

let comProjectH:CGFloat=projectSize.height;

　　//记得要在计算的字符串UILable中加上

　　UIlable.font=UIFont.systemFontOfSize(14);

　　//显示几行

UIlable.numberOfLines=1;

　　UIlable.frame = CGRectMake(50, 50, comProjectW, comProjectH);