日期的一些方法，日期转字符串，字符串转日期，前一个月和后一个月

#pragma mark - date转字符串

-(NSString *)DateToString:(NSDate *)date{

    NSDateFormatter *formatter = [[NSDateFormatteralloc]init];

    [formatter setDateFormat:@"yyyy-MM-dd"];

    NSString *newDataStr = [formatterstringFromDate:date];

    return newDataStr;

}

#pragma mark -字符串转date

-(NSDate *)stringTodate:(NSString *)dateStr{

    NSDateFormatter *format = [[NSDateFormatteralloc]init];

    format.dateFormat =@"yyyy-MM";

    NSDate *date = [formatdateFromString:dateStr];

    return date;

}

#pragma mark - 获取上月或者下个月

- (void)setupRequestMonth:(NSString *)currentDateStr{

    NSDate *currentDate = [NSDate date];

    NSDateFormatter *formatter = [[NSDateFormatteralloc]init];

    [formatter setDateFormat:@"yyyy-MM"];

    

    NSCalendar *calendar = [[NSCalendaralloc]initWithCalendarIdentifier:NSGregorianCalendar];

    NSDateComponents *lastMonthComps = [[NSDateComponentsalloc]init];

    //    [lastMonthComps setYear:1]; // year = 1表示1年后的时间
year = -1为1年前的日期，month day类推

    [lastMonthComps setMonth:-1];//传1就是下一个月

    NSDate *newdate = [calendardateByAddingComponents:lastMonthCompstoDate:currentDateoptions:0];

    NSString *dateStr = [formatterstringFromDate:newdate];

    NSLog(@"date str = %@", dateStr);

}

#pragma mark - 获取当月的第一天和最后一天

- (NSString *)getMonthBeginAndEndWith:(NSString *)dateStr{

    

    NSDateFormatter *format=[[NSDateFormatteralloc]init];

    [format setDateFormat:@"yyyy-MM"];

    NSDate *newDate=[formatdateFromString:dateStr];

    double interval =0;

    NSDate *beginDate =nil;

    NSDate *endDate =nil;

    NSCalendar *calendar = [NSCalendarcurrentCalendar];

    

    [calendar setFirstWeekday:2];//设定周一为周首日

    BOOL ok = [calendarrangeOfUnit:NSMonthCalendarUnitstartDate:&beginDateinterval:&interval
forDate:newDate];

    //分别修改为 NSDayCalendarUnit NSWeekCalendarUnit NSYearCalendarUnit

    if (ok) {

        endDate = [beginDate dateByAddingTimeInterval:interval-1];

    }else {

        return@"";

    }

    NSDateFormatter *myDateFormatter = [[NSDateFormatteralloc]init];

    [myDateFormatter setDateFormat:@"YYYY-MM-dd"];

    NSString *beginString = [myDateFormatterstringFromDate:beginDate];

    NSString *endString = [myDateFormatterstringFromDate:endDate];

    NSString *s = [NSStringstringWithFormat:@"%@----%@",beginString,endString];

    return s;

}