+ (NSString *)getMonthBeginAndEndWith:(NSString *)dateStr{
    
    NSDateFormatter *format=[[NSDateFormatter alloc] init];
    [format setDateFormat:@"yyyy-MM"];
    NSDate *newDate=[format dateFromString:dateStr];
    double interval = 0;
    NSDate *beginDate = nil;
    NSDate *endDate = nil;
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    [calendar setFirstWeekday:2];//設定週一為周首日
    BOOL ok = [calendar rangeOfUnit:NSMonthCalendarUnit startDate:&beginDate interval:&interval forDate:newDate];
    //分別修改為 NSDayCalendarUnit NSWeekCalendarUnit NSYearCalendarUnit
    if (ok) {
        endDate = [beginDate dateByAddingTimeInterval:interval-1];
    }else {
        return @"";
    }
    NSDateFormatter *myDateFormatter = [[NSDateFormatter alloc] init];
    [myDateFormatter setDateFormat:@"YYYY.MM.dd"];
    NSString *beginString = [myDateFormatter stringFromDate:beginDate];
    NSString *endString = [myDateFormatter stringFromDate:endDate];
    NSString *s = [NSString stringWithFormat:@"%@-%@",beginString,endString];
    return s;
}