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PORearranging UITableView with Core Data
 

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    <blockquote> <p><strong>Possible Duplicate:</strong><br> <a href="https://stackoverflow.com/questions/1077568/how-to-implement-re-ordering-of-coredata-records">How to implement re-ordering of CoreData records?</a> </p> </blockquote> <p>I'm trying to find a code sample that shows how to handle moving/rearranging cells in a tableView when the cell uses a fetchedResultsController (i.e. in conjunction with Core Data). I'm getting the moveRowAtIndexPath: call to my data source, but I can't find the right combination of black magic to get the table/data to recognize the change properly.</p> <p>For example, when I move row 0 to row 2 and then let go, it "looks" correct. Then I click "Done". The row (1) that had slid up to fill row 0 still has it's editing mode appearance (minus and move icons), while the other rows below slide back to normal appearance. If I then scroll down, as row 2 (originally 0, remember?) nears the top, it completely disappears.</p> <p>WTF. Do I need to somehow invalidate the fetchedResultsController? Whenever I set it to nil, I get crashes. Should I release it instead? Am I in the weeds?</p> <p>Here's what I've currently got in there...</p> <pre><code>- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath { NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; /* Update the links data in response to the move. Update the display order indexes within the range of the move. */ if (fromIndexPath.section == toIndexPath.section) { NSInteger start = fromIndexPath.row; NSInteger end = toIndexPath.row; NSInteger i = 0; if (toIndexPath.row &lt; start) start = toIndexPath.row; if (fromIndexPath.row &gt; end) end = fromIndexPath.row; for (i = start; i &lt;= end; i++) { NSIndexPath *tempPath = [NSIndexPath indexPathForRow:i inSection:toIndexPath.section]; LinkObj *link = [fetchedResultsController objectAtIndexPath:tempPath]; //[managedObjectContext deleteObject:[fetchedResultsController objectAtIndexPath:tempPath]]; link.order = [NSNumber numberWithInteger:i]; [managedObjectContext refreshObject:link mergeChanges:YES]; //[managedObjectContext insertObject:link]; } } // Save the context. NSError *error; if (![context save:&amp;error]) { // Handle the error... } } - (void)controllerWillChangeContent:(NSFetchedResultsController *)controller { // The fetch controller is about to start sending change notifications, so prepare the table view for updates. if (self.theTableView != nil) [self.theTableView beginUpdates]; } - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller { // The fetch controller has sent all current change notifications, so tell the table view to process all updates. if (self.theTableView != nil) { [self.theTableView endUpdates]; } } </code></pre>
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    1. USGreg Combs
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    1. COI worked this out a bit differently (will post when it is tested). Whats really needed for this is a "Reverse-NSFetchedResultsController". Essentially feed an NSFetchedResultsController a UITableView, a sort order, and section headers, and have it write everything back to CoreData. I think I might try to put this together for fun.
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      1. USCorey Floyd
    2. COAbsolutely ... something a little more elegant than my solution that will allow a bidirectional synch between the stored data and the table user interface. I'd love to see what you come up with when you're done.
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      1. USGreg Combs
    3. COFor what it's worth, Matt Long recently posted a nice tutorial on re-ordering the rows in an NSFetchedResultsController-backed table: http://www.cimgf.com/2010/06/05/re-ordering-nsfetchedresultscontroller
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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