iOS7之前localNotification.repeatInterval = NSWeekCalendarUnit可以设置按周提醒。iOS7之后NSWeekCalendarUnit被去掉
取而代之的是NSCalendarUnitWeekOfMonth和NSCalendarUnitWeekOfYear

但是使用NSCalendarUnitWeekOfMonth时next fire date = null 到时候并不提醒
NSCalendarUnitWeekOfYear正常

NSCalendarUnit包含的值有：
        NSCalendarUnitEra                 -- 
        NSCalendarUnitYear                -- 年单位。相当于经历了多少年，未来多少年。
        NSCalendarUnitMonth               -- 月单位。范围为1-12
        NSCalendarUnitDay                 -- 按天重复。范围为1-31
        NSCalendarUnitHour                -- 每小时提醒。范围为0-24
        NSCalendarUnitMinute              -- 每分钟提醒。范围为0-60
        NSCalendarUnitSecond              -- 秒单位。范围为0-60
        NSCalendarUnitWeekday             -- 星期单位，每周的7天。范围为1-7
        NSCalendarUnitWeekdayOrdinal      -- 
        NSCalendarUnitQuarter             -- 几刻钟，也就是15分钟。范围为1-4
        NSCalendarUnitWeekOfMonth         -- 一个月每周提醒。最多为6个周
        NSCalendarUnitWeekOfYear          -- 一年每周提醒。范围为1-53 最多为53个周
        NSCalendarUnitYearForWeekOfYear   -- 
        NSCalendarUnitTimeZone            -- 

1.计算出要提醒的日期

// weekDay代表设置的哪天要提醒
- (NSDate *)setDateForAlarmWithWeekday:(NSInteger)weekDay settingTime:(NSString*)timeString
{
    NSCalendar *calendar = [NSCalendar currentCalendar];
    [calendar setTimeZone:[NSTimeZone defaultTimeZone]];
    
    unsigned currentFlag = NSCalendarUnitDay|NSCalendarUnitMonth|NSCalendarUnitYear|NSCalendarUnitWeekday;
    
    NSDateComponents *comp = [calendar components:currentFlag fromDate:[NSDate date]];
    
    NSInteger hour = [[[timeString componentsSeparatedByString:@":"] objectAtIndex:0] intValue];
    NSInteger min = [[[timeString componentsSeparatedByString:@":"] objectAtIndex:1] intValue];
    
    comp.hour = hour;
    comp.minute = min;
    comp.second = 0;
    
    NSInteger diff = (weekDay - comp.weekday);
    
    NSInteger multiplier;
    if (weekDay == 0) {
        multiplier = 0;
    }else {
        //今天注册今天提醒
        multiplier = diff > 0 ? diff:(diff == 0 ? diff : diff+7);

//        multiplier = diff > 0 ? diff:diff+7;
    }
    
    return [[calendar dateFromComponents:comp] dateByAddingTimeInterval:multiplier*3600*24];
}

2.注册多个通知，礼拜一注册个，礼拜三注册一个

- (void)notificationWithDate:(NSDate *)date time:(NSString *)time{
    UILocalNotification *localNotification = [[UILocalNotification alloc] init];
    localNotification.fireDate = date;
    localNotification.timeZone = [NSTimeZone defaultTimeZone];
    localNotification.repeatCalendar = [NSCalendar currentCalendar];
    NSString *alertBody = F(@"%@了，该睡觉了!", time);
    localNotification.alertBody = alertBody;
    localNotification.soundName = UILocalNotificationDefaultSoundName;
    localNotification.repeatInterval = NSCalendarUnitWeekOfYear;
    
    NSDictionary *infoDict = @{@"notif":@"GoodnightCall"};
    localNotification.userInfo = infoDict;
    [[UIApplication sharedApplication] scheduleLocalNotification:localNotification];

}