每月更新coredata对象

Question

in a current project i manage entities Month that contain information about passed month' and one of them of course stands for the current month.

every month contains a number attribute, that acts as identifier for the year. the attribute contains an NSNumber of type int32 , that identifies the month with the format: YYYYMM . so for example February 2011 has the attribute number = 201102 .

in the application the user enters data, that is always afflicted with the current month. the user does not have the ability to edit, delete, or add month data of passed month.

so my coredata holds 1 month for the current month that will be updated, and as many other objects as month have passed in which the user has entered data.

i have a function

-(void)archiveMonth:(NSNumber *)month;

in my DAO class, that creates a new month object in coredata or updates the current month if the passed NSNumber matches the current month.

here comes the tricky part

every time the user opens the application for the first time in a new month, i need the application to archive all passed month that dont have a corresponding core-data object yet.

how i did it so far (for testing purposes) looks like that:

    NSDate *rootDate = [NSDate dateWithTimeIntervalSinceReferenceDate:(10*365*24*60*60)];
    // somewhere in 2010 so to be sure to catch all passed month

    NSNumber *rootMonth = [dataHandler getMonthNumber:rootDate] ;
    NSNumber *iterator;   // acts as the monthnumber currently active in the loop
    int now = [dataHandler getMonthNumber:[NSDate date]].intValue;

    iterator = [NSNumber numberWithInt:rootMonth.intValue];
    while (now >= iterator.intValue) {
        iterator = [NSNumber numberWithInt:iterator.intValue+1];
        if (iterator.intValue%100 > 12) { //jump all invalid month numbers 

            while (iterator.intValue%100 != 1) {
                iterator = [NSNumber numberWithInt:iterator.intValue+1 ];
            }
        }

        NSArray *temp = [dataHandler fetchMonth:iterator];
        if (temp.count == 0) {                         
            //  no data = needs archive
            [dataHandler archiveMonth:iterator];
        }
    }

i have this in my factory that gets called at application start.

questions this is very ugly and creates a lot of overhead

• how can i determine if its the first time in the month the user opens the app so i dont have to archive every single time he starts the app?
• do any of you see a better way to iterate through passed month?
• might there even be a way i dont have to fetch every month to determine if it already exists?
• can i somehow find out what was the last month archived, and start the iteration from there?

i would really appreciate some help, thanks in advance =) if you need any more code, or find something might be missing in the question, ill be happy to provide it.

note this is a mockup code, that i used for testing, the question is not how to improve the code, but how to improve the algorithm =)

Answer 1

I would do it this way:

1. Run your monthly check and store the yyyyMM value to NSUserDefaults .
2. Every application launch, calculate the yyyyMM value for the current date and compare it to the value stored in NSUserDefaults .
3. If it doesn't match, then it is a new month so run your monthly checks again.

It looks like this:

#define KEY_FOR_MONTHLY_LAST_CHECKED @"monthlyCheckedKey"

- (NSInteger)yyyyMMFromDate:(NSDate *)date {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyyMM"];

    NSString *yyyyMMString = [formatter stringFromDate:date];
    return [yyyyMMString intValue];
}

- (void)runMonthly {
    // This code is run once per month

    // Update NSUserDefaults
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setInteger:[self yyyyMMFromDate:[NSDate date]] forKey:KEY_FOR_MONTHLY_LAST_CHECKED];
    [defaults synchronize];
}

- (void)checkMonthly {
    NSUserDefaults *defaults    = [NSUserDefaults standardUserDefaults];
    NSInteger lastCheckedyyyyMM = [defaults integerForKey:KEY_FOR_MONTHLY_LAST_CHECKED];
    NSInteger currentyyyyMM     = [self yyyyMMFromDate:[NSDate date]];

    if (lastCheckedyyyyMM != currentyyyyMM) {
        [self runMonthly];
    }
}

All you have to do is add [self checkMonthly]; so that it runs every application launch.

Also, I would change this:

if (iterator.intValue%100 > 12) { //jump all invalid month numbers 
    while (iterator.intValue%100 != 1) {
        iterator = [NSNumber numberWithInt:iterator.intValue+1 ];
    }
}

To this:

if (iterator.intValue % 100 == 13) { //jump all invalid month numbers 
    iterator = [NSNumber numberWithInt:iterator.intValue+88];
}

It just adds 87 to the number when it hits 13 to change something like 201113 to 201201