计算字符串的高度

extension String {

//////

/// @brief 获取字符串的高度

/// @param fontSize 字体大小

/// @param width 限制一行显示的宽度

/// @return 返回文本在width宽度的条件下的总高度

///

func height(let fontSize: CGFloat, let width: CGFloat) ->CGFloat {

let font = UIFont.systemFontOfSize(fontSize)

let size = CGSizeMake(width, CGFloat.max)

var style = NSMutableParagraphStyle()

style.lineBreakMode = NSLineBreakMode.ByCharWrapping

var attributes = [NSFontAttributeName: font, NSParagraphStyleAttributeName: style.copy()];

// 强转成NSString

var text = self as NSString

var rect = text.boundingRectWithSize(size,

options: NSStringDrawingOptions.UsesLineFragmentOrigin,

attributes: attributes,

context: nil)

return rect.size.height

}