lable boundingRectWithSize IOS6

最近项目需要支持IOS6.0系统，lable计算会出现问题，先对lable 使用category，重写boundingRectWithSize，判断系统版本号，然后在调用不同的方法
if (IOS5) {
NSInteger width = size.width;
CGSize retSize = [self.textsizeWithFont:self.fontconstrainedToSize:CGSizeMake(width,MAXFLOAT)
lineBreakMode:NSLineBreakByWordWrapping];
//适配IOS6
// CGSize retSize = [self.text sizeWithFont:self.font constrainedToSize:size lineBreakMode:NSLineBreakByCharWrapping];
return retSize;
}else{
NSDictionary *attribute =@{NSFontAttributeName:self.font};
CGSize retSize = [self.textboundingRectWithSize:size

options:\
NSStringDrawingTruncatesLastVisibleLine |
NSStringDrawingUsesLineFragmentOrigin |
NSStringDrawingUsesFontLeading

attributes:attribute

context:nil].size;
return retSize;
}