给字体加粗

#define IOS_VERSION [[[UIDevice currentDevice] systemVersion] floatValue]

 if(IOS_VERSION >= 8.0)
        {
            lbl_title.font = [UIFont systemFontOfSize:14 weight:1];
        }
        else
        {
            lbl_title.font = [UIFont systemFontOfSize:14];
        }