iOS开发之获得当前时间的前几天，几个月，几年

不说前言，上来就干记录一下

        //得到当前的时间
        NSDate * mydate = [NSDate date];
      
        NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"yyyy-MM-dd"];
        NSString *currentDateStr = [dateFormatter stringFromDate:[NSDate date]];
        DebugLog(@"---当前的时间的字符串 =%@",currentDateStr);
        NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
        
        NSDateComponents *comps = nil;
        
        comps = [calendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitMonth fromDate:mydate];
        
        NSDateComponents *adcomps = [[NSDateComponents alloc] init];
        
        [adcomps setYear:0];
        
        [adcomps setMonth:-2];
        
        [adcomps setDay:0];
        NSDate *newdate = [calendar dateByAddingComponents:adcomps toDate:mydate options:0];
        NSString *beforDate = [dateFormatter stringFromDate:newdate];
        DebugLog(@"---前两个月 =%@",beforDate);