- (void)viewWillAppear:(BOOL)animated
{
if (_needRefresh)
{ NSLog(#"Type This If You Are IN");
[self.myTableView reloadSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:UITableViewRowAnimationFade];
_needRefresh = NO;
}
I want to refresh my table only if something is changed. the code [self.myTableView reloadSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:UITableViewRowAnimationFade]; works great when I move to the viewController but when I put it inside if something is going wrong. I can see that the NSLog from inside the if is printed so I don't understand what's the difference and why the reloading is not getting executed.
Related
I'm getting a crash when trying to access an object in NSFetchedResultsController.
2013-11-10 15:15:06.568 Social[11503:70b] CoreData: error: Serious application error. Exception was caught during Core Data change processing. This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification. *** -[__NSArrayI objectAtIndex:]: index 2 beyond bounds for empty array with userInfo (null)
2013-11-10 15:15:06.570 Social[11503:70b] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayI objectAtIndex:]: index 2 beyond bounds for empty array'
viewDidLoad
- (void)viewDidLoad
{
[super viewDidLoad];
self.resultController = [DataEngine sharedInstance].postsFetchedResultController;
self.resultController.delegate = self;
[self.resultController performFetch:nil];
[self.tableView reloadData];
[[DataEngine sharedInstance] fetchInBackground];
}
Result Controller Delegate
#pragma mark - NSFetchedResultsControllerDelegate Methods -
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView beginUpdates];
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller
didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
switch (type)
{
case NSFetchedResultsChangeInsert:
[self.tableView insertRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeUpdate:
[self.tableView reloadRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeMove:
[self.tableView moveRowAtIndexPath:indexPath toIndexPath:newIndexPath];
break;
default:
break;
}
}
table view
#pragma mark - UITableView Delegate & Datasrouce -
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return self.resultController.fetchedObjects.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
return [self cellForRowAtIndexPath:indexPath];
}
One reason for crash on below line could be that you are updating self.resultContrlller after you have used it for retuning the number of rows of your table section. Make sure that if you are constantly updating your self.resultContrlller object then you take a copy of it and then use for your table drawing.
// This code does not prevent crash. Changing your regular code to modern objective-C way
Post *post = [self.resultContrlller fetchedObjects][indexPath.row];
The data source should not change while table is reloading itself. You should use a copy of fetchedObjects instead to load the table. So, evey time, before you reload your table, take a copy [[self.resultContrlller fetchedObjects] copy] and the use it for table drawing. Your main source can then keep on changing. And after table reload is done with copy you may want to reload it it again if there was a change in the data. Such crashes happens when your data source changes faster than table reloads.
In one of my NSManagedObject subclasses I had the follwiing code which was causing the issue. NSSets are automatically initialized on NSManagedObejcts and there is no need to initialize them.
- (void)awakeFromFetch
{
if (!self.comments)
self.comments = [NSMutableSet set];
if (!self.medias)
self.medias = [NSMutableSet set];
}
Another problem was that during insert indexPath is null, I had to use newIndexPath instead
case NSFetchedResultsChangeInsert:
[self.tableView insertRowsAtIndexPaths:#[newIndexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
I have a very frustrating issue. I have an app with a UITableView.
When I am removing a cell from the table view, it is removed from the data model and then I call the following:
-(void)removeItem:(NSIndexPath *)indexPath {
[self.tableView beginUpdates];
[self.tableView deleteRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationRight];
[self.tableView endUpdates];
}
My problem is, I've tried it like I do above, and I've tried without using animateWithDuration. I've even tried with a CATransaction, but however I do it, the animation doesn't happen.
I've got slow animations on in my Simulator and when I remove an item from the list, it removes correctly, but without animation.
It just disappears and leaves a blank space for a moment before the table view data is reloaded.
I've search all over SO and Google and I can't seem to find an answer.
Any ideas?
Does it perhaps have to do with the fact that I'm removing the object from the data model before calling the function above?
Edit: Removed the Animation Block as it is incorrect
According to THIS you don't need to use the animateWithDuration:animations: at all.
Just try it like this
-(void)removeItem:(NSIndexPath *)indexPath {
[self.tableView beginUpdates];
[self.tableView deleteRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationRight];
[self.tableView endUpdates];
}
Okay, I don't know if it's just bad manners, but I feel I'm going to answer my own question here.
First, thanks for all the other answers, you were all correct of course, but none of the answers solved my problem.
It turns out that there is another area in the code that does a different check then calls one of the tableView delegate methods, that seems to cancel the animation.
So the answer is as follows:
When you're row is removing but the animations aren't working, make sure that you are not calling didSelectRowAtIndexPath:indexPath before the animation starts. This will cancel the animations.
If you're NOT having that problem, here's some really typical code for expanding, two lines in the example:
Note that facebookRowsExpanded is a class variable you must have:
if ( [theCommand isEqualToString:#"fbexpander"] )
{
NSLog(#"expander button......");
[tableView deselectRowAtIndexPath:indexPath animated:NO];
NSArray *deleteIndexPaths;
NSArray *insertIndexPaths;
facebookRowsExpanded = !facebookRowsExpanded;
// you must do that BEFORE, not AFTER the animation:
if ( !facebookRowsExpanded ) // ie, it was just true, is now false
{
deleteIndexPaths = [NSArray arrayWithObjects:
[NSIndexPath indexPathForRow:2 inSection:0],
[NSIndexPath indexPathForRow:3 inSection:0],
nil];
[tableView beginUpdates];
[tableView
deleteRowsAtIndexPaths:deleteIndexPaths
withRowAnimation: UITableViewRowAnimationMiddle];
[tableView endUpdates];
}
else
{
insertIndexPaths = [NSArray arrayWithObjects:
[NSIndexPath indexPathForRow:2 inSection:0],
[NSIndexPath indexPathForRow:3 inSection:0],
nil];
[tableView beginUpdates];
[tableView
insertRowsAtIndexPaths:insertIndexPaths
withRowAnimation: UITableViewRowAnimationMiddle];
[tableView endUpdates];
}
// DO NOT do this at the end: [_superTableView reloadData];
return;
}
NOTE: your code for numberOfRowsInSection must use facebookRowsExpanded
(it will be something like "if facebookRowsExpanded return 7, else return 5")
NOTE: your code for cellForRowAtIndexPath must use facebookRowsExpanded.
(it has to return the correct row, depending on whether or not you are expanded.)
First, you don't need to animate the change yourself.
Second, I think you need to make the changes to the datasource between the begin and end updates.
Your method should look something like this:
-(void)removeItemAtIndexPath:(NSIndexPath *)indexPath{
[self.tableView beginUpdates];
// I am assuming that you're just using a plain NSMutableArray to drive the data on the table.
// Delete the object from the datasource.
[self.dataArray removeObjectAtIndex:indexPath.row];
// Tell the table what has changed.
[self.tableView deleteRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationRight];
[self.tableView endUpdates];
}
[self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];
[self.tableView deleteRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];
[self.tableView endUpdates];
indexPaths is an array of NSIndexPaths to be inserted or to be deleted in your table.
NSarray *indexPaths = [[NSArray alloc] initWithObjects:
[NSIndexPath indexPathForRow:0 inSection:0],
[NSIndexPath indexPathForRow:1 inSection:0],
[NSIndexPath indexPathForRow:2 inSection:0],
nil];
I have a UITableView that uses an NSFetchedResultsController as data source.
The core data store is updated in multiple background threads running in parallel (each thread using it's own NSManagedObjectContext).
The main thread observes the NSManagedObjectContextDidSaveNotification
notification and updates it's context with mergeChangesFromContextDidSaveNotification:.
Sometimes it happens that the NSFetchedResultsController sends an
NSFetchedResultsChangeUpdate event with an indexPath that does not exist
anymore at that point.
For example: The result set of the fetched results controller contains
1 section with 4 objects. The first object is deleted in one thread.
The last object is updated in a different thread. Then sometimes the
following happens:
controllerWillChangeContent: is called.
controller:didChangeObject:atIndexPath:forChangeType:newIndexPath: is called with
type = NSFetchedResultsChangeDelete, indexPath.row = 0.
controller:didChangeObject:atIndexPath:forChangeType:newIndexPath: is called with
type = NSFetchedResultsChangeUpdate, indexPath.row = 3.
But the fetched results controller contains only 3 objects now, and if call
MyManagedObject *obj = [controller objectAtIndexPath:indexPath]
to update the table view cell according to the NSFetchedResultsChangeUpdate
event, this crashes with a NSRangeException exception.
Thank you for any help or ideas!
I have now found a solution for my problem. In the case of an update event, there is no need to call
[self.controller objectAtIndexPath:indexPath]
because the updated object is already supplied as the anObject parameter to the -controller:didChangedObject:... delegate.
I have therefore replaced -configureCell:atIndexPath: by a -configureCell:withObject: method that uses the updated object directly. This seems to work without problems.
The code looks now like this:
- (void)configureCell:(UITableViewCell *)cell withObject:(MyManagedObject *)myObj
{
cell.textLabel.text = myObj.name;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"MyCellIdentifier"];
[self configureCell:cell withObject:[self.controller objectAtIndexPath:indexPath]];
return cell;
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type) {
/* ... */
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath] withObject:anObject];
break;
/* ... */
}
}
This is actually quite common because of the bug in Apple's boiler plate code for NSFetchedResultsControllerDelegate, which you get when you create a new master/detail project with Core Data enabled:
- (void)controller:(NSFetchedResultsController *)controller
didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath
forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath]
atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
Solution #1: Use anObject
Why query the fetched results controller and risk using an incorrect index path when the object is already given to you? Martin R recommends this solution as well.
Simply change the helper method configureCell:atIndexPath: from taking an index path to take in the actual object that was modified:
- (void)configureCell:(UITableViewCell *)cell withObject:(NSManagedObject *)object {
cell.textLabel.text = [[object valueForKey:#"timeStamp"] description];
}
In cell for row, use:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
[self configureCell:cell withObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];
return cell;
}
Finally, in the update use:
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath]
withObject:anObject];
break;
Solution #2: Use newIndexPath
As of iOS 7.1, both indexPath and newIndexPath are passed in when a NSFetchedResultsChangeUpdate happens.
Simply keep the default implementation's usage of indexPath when calling cellForRowAtIndexPath, but change the second index path that is sent in to newIndexPath:
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath]
atIndexPath:newIndexPath];
break;
Solution #3: Reload rows at index path
Ole Begemann's solution is to reload the index paths. Replace the call to configure cell with a call to reload rows:
case NSFetchedResultsChangeUpdate:
[tableView reloadRowsAtIndexPaths:#[indexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
There are two disadvantages with this method:
By calling reload rows, it will call cellForRow, which in turn calls dequeueReusableCellWithIdentifier, which will reuse an existing cell, possibly getting rid of important state (e.g. if the cell is in the middle of being dragged a la Mailbox style).
It will incorrectly try and reload a cell that isn't visible. In Apple's original code, cellForRowAtIndexPath: will return "nil if the cell is not visible or indexPath is out of range." Therefore it would be more correct to check with indexPathsForVisibleRows before calling reload rows.
Reproducing the bug
Create a new master/detail project with core data in Xcode 6.4.
Add a title attribute to the core data event object.
Populate the table with several records (e.g. in viewDidLoad run this code)
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
for (NSInteger i = 0; i < 5; i++) {
NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];
[newManagedObject setValue:[NSDate date] forKey:#"timeStamp"];
[newManagedObject setValue:[#(i) stringValue] forKey:#"title"];
}
[context save:nil];
Change configure cell to show the title attribute:
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.textLabel.text = [NSString stringWithFormat:#"%# - %#", [object valueForKey:#"timeStamp"], [object valueForKey:#"title"]];
}
In addition to adding a record when the new button is tapped, update the last item (Note: this can be done before or after the item is created, but make sure to do it before save is called!):
// update the last item
NSArray *objects = [self.fetchedResultsController fetchedObjects];
NSManagedObject *lastObject = [objects lastObject];
[lastObject setValue:#"updated" forKey:#"title"];
Run the app. You should see five items.
Tap the new button. You will see that a new item is added to the top, and that the last item does not have the text "updated," even though it should have had it. If you force the cell to reload (e.g. by scrolling the cell off the screen), it will have the text "updated."
Now implement one of the three solutions outlined above and in addition to an item being added, the last item's text will change to "updated."
i have read a lot on this argument, i have tested this example that works:
source code example. but this doesn't use storyboards (i don't know if this is the reason that make my project not working)
i have made another project using storyboard, the same sequence of instruction doesn't work...
-(void)viewDidAppear:(BOOL)animated{
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:1 inSection:0];
[firstController.tableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
[firstTable.delegate tableView:firstTable didSelectRowAtIndexPath:indexPath];
}
here is my project, is the same of the previous link, only adding viewDidAppear
my not working project
can someone tell me what's wrong?
thanks
I tried to study your code downloading the project.The problem is that firstController.tableView is nil.
So fix it:
[firstTable selectRowAtIndexPath:indexPath
animated:NO
scrollPosition:UITableViewScrollPositionNone];
Or assign firstController.tableView to the table view.
- (void)viewDidLoad {
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] animated:NO scrollPosition:UITableViewScrollPositionNone];
}
If you want the callback from the delegate:
if ([self.tableView.delegate respondsToSelector:#selector(tableView:didSelectRowAtIndexPath:)]) {
[self.tableView.delegate tableView:self.tableView didSelectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]];
}
I have an UITableViewController which is backed by an NSFetchedResultsController.
My NSFetchedResultsController put results into two sections based on a boolean.
In a background thread, the datasource is altered such that rows are added or removed.
I have my background thread's NSManagedObjectContext's merging correctly and this situation work fine for most cases. Rows alter when the data is changed and move between sections with animations.
There is one situation however where my application crashes with an EXC_BAD_ACCESS.
The case is when the last row in a section is moved to the other section. (Stack trace below). The crash occurs in objc_msgSend but the normal debugging tips I use aren't returning anything helpful, I simply receive "Value can't be converted to integer" from gdb.
The NSFetchedResultsControllerDelegate methods get called in the following order:
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller;
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type;
// ^ The parameters specify a deletion of the 1st section
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath;
// ^ The parameters specify a moved row from the 1st section to the 1st section
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller;
Looking through StackOverflow, many of the people who encounter similar issues are backing their UITableViewController manually using an NSArray or NSMutableArray and they're simply not updating the datasource at the correct time. In this case the NSFetchedResultsController is handling returning the number of rows and sections and is definitely updated by the time the [tableView endUpdates] is called.
Has anyone got any debugging tips, pointers or solutions?
This blog post hints at working around a similar problem where a new section is created.
I have two options if I cannot solve this issue as is:
Forgo animation on rows and simply call [tableView reloadData]
Switch to using NSArray backed storage for the UITableView and hope for the best
Update
I have modified the Apple sample Core Data application "Locations" to use an NSFetchedResultsController directly and reproduced the issue.
I have uploaded the source code for this project. Use that project to reproduce the issue.
Simply click the + button a few times and wait
Every 5 seconds an item gets moved to another category.
When the first category is about to be emptied, it crashes.
The crash is sometimes about creating two animations for the same cell as per other StackOverflow questions on the topic. More commonly the crash is as discussed above and below.
Reference
The stack trace:
#0 0x31e0afbc in objc_msgSend ()
#1 0x32c11522 in -[_UITableViewUpdateSupport(Private) _computeRowUpdates] ()
#2 0x32c10510 in -[_UITableViewUpdateSupport initWithTableView:updateItems:oldRowData:newRowData:oldRowRange:newRowRange:context:] ()
#3 0x32c0f99e in -[UITableView(_UITableViewPrivate) _endCellAnimationsWithContext:] ()
#4 0x32c0e66c in -[UITableView endUpdatesWithContext:] ()
#5 0x000088d6 in -[DraftHistoryController controllerDidChangeContent:] (self=0x3f6f1e0, _cmd=0x377ca29c, controller=0x3f716e0) at /Users/ataylor/Documents/Documents/Programming/iPhone/Drafter/Drafter/Drafter/DraftHistoryController.m:323
#6 0x3775a892 in -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:] ()
My NSFetchedResultsControllerDelegate methods are the same ones from the Apple sample code:
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller is about to start sending change notifications, so prepare the table view for updates.
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
// Reloading the section inserts a new row and ensures that titles are updated appropriately.
[tableView reloadSections:[NSIndexSet indexSetWithIndex:newIndexPath.section] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller has sent all current change notifications, so tell the table view to process all updates.
[self.tableView endUpdates]; // <---- Crash occurs here
}
The relevant UITableViewControllerDelegate methods are as follows:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [[self.fetchedResultsController sections] count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
I took a quick look. Your modified Locations project didn't crash on me but it did generate core data exceptions. The problem lies in reloading the sections in controller:didChangeObject:. I changed the code as follows and everything looks good to me (including the section titles) on both iOS 4.3 and iOS 5.
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type) {
// other cases here
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
I was super curious about the code that fixed an issue with adding a new section so I decided to pop it in place of my current NSFetchedResultsControllerDelegate methods and it indeed solved my problem. Tracing through, I have discovered that this code from the Apple "Locations" sample crashes when using the NSFetchedResultsController:
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
// Reloading the section inserts a new row and ensures that titles are updated appropriately.
[tableView reloadSections:[NSIndexSet indexSetWithIndex:newIndexPath.section] withRowAnimation:UITableViewRowAnimationFade];
break;
But the following code works perfectly:
case NSFetchedResultsChangeMove:
if (newIndexPath != nil) {
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView insertRowsAtIndexPaths: [NSArray arrayWithObject:newIndexPath] withRowAnimation: UITableViewRowAnimationTop];
}
else {
[self.tableView reloadSections:[NSIndexSet indexSetWithIndex:[indexPath section]] withRowAnimation:UITableViewRowAnimationFade];
}
break;
I don't have a case where section headings will change, I won't continue debugging to solve the issue Apple's code purports to fix around section titles.
Because every question needs a swift answer, here's one (based on XJones's accepted answer). As is the case with the other answers, the magic is in the .Move: delete and insert instead of moving the row.
This is my NSFRC delegate didChangeObject:
func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
switch type {
case .Delete:
if let deletePath = indexPath {
self.tableView.deleteRowsAtIndexPaths([deletePath], withRowAnimation: .None)
}
break
case .Insert:
if let insertPath = newIndexPath {
self.tableView.insertRowsAtIndexPaths([insertPath], withRowAnimation: .Fade)
}
break
case .Update:
if let updatePath = indexPath {
self.tableView.reloadRowsAtIndexPaths([updatePath], withRowAnimation: .None)
}
break
case .Move:
if let indexPath = indexPath, newIndexPath = newIndexPath {
self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
self.tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
}
break
}
}
I was getting a crash overtime I deleted the last row in a section.
Do make sure you have implemented controller:didChangeSection:atIndex:forChangeType: to handle section removal.
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.viewTable insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.viewTable deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}