Question

Scenario:

I have an expense tracking iOS Application and I am storing expenses from a expense detail view controller into a table view (with fetched results controller) that shows the list of expenses along with the category and amount and date. I do have a date attribute in my entity “Money” which is a parent entity for either an expense or an income.

My Question:

What I want is to basically categorize my expenses/incomes for a given week, a month, or year and display it as the section header title for example : (Oct 1- Oct 7, 2012) and it shows expenses/incomes amount and related stuff according to that particular week. Two buttons are provided in that view, if I would press the right button, it will increment the week by a week (Oct 1- Oct 7, 2012 now shows Oct8 – Oct 15, 2012) and similarly the left button would decrement the week by a week. I have two segment controls in the view as well. What I want to do is press the segment control which says “weekly” and if I press another segment which says “category” – how would I filter out my expenses/incomes per week based on category ?

I want to display two sections in my table view (one which shows the date for expenses and another to show the date for incomes in format (Oct1,2012 – Oct7, 2012)). How would I achieve this? I have written some pseudo code and if anybody can tell me how would I accomplish the above, that would be great.

EDIT – FETCH CONTROLLER

- (void)userDidSelectStartDate:(NSDate *)startDate andEndDate:(NSDate *)endDate
{    
    AppDelegate * applicationDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
    NSManagedObjectContext * context = [applicationDelegate managedObjectContext];

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Money" inManagedObjectContext:context];
    [fetchRequest setEntity:entity];

    [NSFetchedResultsController deleteCacheWithName:nil];

    //Here you create the predicate that filters the results to only show the ones with the selected date
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(date >= %@) AND (date <= %@)", startDate, endDate];
    [fetchRequest setPredicate:predicate];

    // Set the batch size to a suitable number.
     [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.

    NSSortDescriptor * sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"type" ascending:YES];

    NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];

    NSSortDescriptor *sortDescriptor3 = [[NSSortDescriptor alloc] initWithKey:@"cat" ascending:YES];

    NSArray * descriptors = [NSArray arrayWithObjects:sortDescriptor1, sortDescriptor2, sortDescriptor3, nil];

    [fetchRequest setSortDescriptors:descriptors];
    [fetchRequest setIncludesSubentities:YES];
    [fetchRequest setResultType:NSManagedObjectResultType];

    if(_fetchedResultsController)
    {
          [_fetchedResultsController release]; _fetchedResultsController = nil;

    }
    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:@"type" cacheName:nil];

    _fetchedResultsController.delegate = self;

    NSError *anyError = nil;

    if(![_fetchedResultsController performFetch:&anyError])
    {
        NSLog(@"error fetching:%@", anyError);
    }

    [sortDescriptor1 release];
    [sortDescriptor2 release];
    [sortDescriptor3 release];

    [fetchRequest release];

     //Finally you tell the tableView to reload it's data, it will then ask your NEW FRC for the new data
    [self.dashBoardTblView reloadData];

}

EDIT – Fetch Controller Delegate Methods

- (void)controllerWillChangeContent:(NSFetchedResultsController*)controller
{
     [self.dashBoardTblView beginUpdates];

}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
       atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

   switch(type) {
    case NSFetchedResultsChangeInsert:
        [self.dashBoardTblView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
                      withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeDelete:
        [self.dashBoardTblView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
                      withRowAnimation:UITableViewRowAnimationFade];
        break;
   }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath{

    switch(type) {
    case NSFetchedResultsChangeInsert:

        [self.dashBoardTblView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeDelete:

        [self.dashBoardTblView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeMove:

        [self.dashBoardTblView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
                         withRowAnimation:UITableViewRowAnimationFade];
        [self.dashBoardTblView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
                         withRowAnimation:UITableViewRowAnimationFade];


        break;

    case NSFetchedResultsChangeUpdate:
    {
        [self.dashBoardTblView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
        break;
    }
  }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [self.dashBoardTblView endUpdates];
} 

Answer 1

To group the “Expense”/”Income” objects into different sections, you need to add a type attribute to the Money entity, for example a Integer attribute that is 0 for expenses and 1 for incomes.

To sort the table view sections by type (expense/income), use type as first sort descriptor:

NSSortDescriptor *s1 = [[NSSortDescriptor alloc] initWithKey:@"type" ascending:YES];

To sort the entries within each section by date, use date as second sort descriptor:

NSSortDescriptor *s2 = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];

NSArray *descriptors = [NSArray arrayWithObjects:s1, s2, nil];
[fetchRequest setSortDescriptors:descriptors];

Finally, to group the table view into sections by category, use type as sectionNameKeyPath:

NSFetchedResultsController *aFetchedResultsController =
   [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                       managedObjectContext:context
                                         sectionNameKeyPath:type
                                                  cacheName:nil];

This should give 2 sections, with all expenses in the first section and all incomes in the second section.

Now for the section headers you have to implement tableView:viewForHeaderInSection: (I hope that I get this right):

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
    id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
    Money *money = [[sectionInfo objects] objectAtIndex:0]; // The first object in this section
    NSNumber *type = money.type;
    if (type.intValue == 0) {
        // Create and return header view for "expense" section.

    } else {
        // Create and return header view for "incomes" section.

    }
}