iOS计算文字尺寸的方法

/**
计算文字的尺寸
*/
- (CGSize)sizeWithText:(NSString *)text font:(UIFont *)font maxSize:(CGSize)maxSize
{
NSDictionary *attrs = @{NSFontAttributeName: font};
return  [text boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;
}