I have an iPad app with ARC, storyboards, supporting ios5+.
I have a VC that is working with NSFetchedResultsController on its own.
The VC has two tableviews pointing at two different entities.
I have single record add, change, delete, and moving of rows working fine on this VC.
I've now introduced a new feature to enable the user to quick add multiple rows to these tableviews.
I do this by providing a segue (modal) from this VC to a new VC (lets call it quickAddVC).
The user enters the data on quickAddVC, and then I segue back (modal) to the original VC.
I save the new records (via an alternate call) before (I believe) setting up the NSFetchedResultsControllers for the VC again (I set them to nil in ViewDidUnload).
However I keep getting this mismatch error.
Somehow it keeps registering the number of inserts that occur from the quickAddVC as 1 insert no matter how many records I add, and it somehow remembers how many records were in the NSFetchedResultsControllers before my segues to do this comparison.
Error:
* Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit/UIKit-2372/UITableView.m:1070
Failure in didChangeObject, name=NSInternalInconsistencyException reason=Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (5) must be equal to the number of rows contained in that section before the update (2), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).
Any ideas on what I am doing wrong or should try would be useful.
I can't figure out how to get the NSFetchedResultsControllers to simply forget its original state and restart from scratch which would I think resolve this issue for me.
I haven't posted any of the code, I guess I could post a lot if needed but hoping there is enough here to outline the design issue and get some ideas.
Just reposting the answer to mark question as closed.
Ok solved the issue. Basically I was clearing the NSFetchedResultsControllers in the wrong place. By setting them to nil just prior to the segue all works fine. I'd made an incorrect assumption that given the ViewDidLoad method was being called when I segued back again, that the ViewDidUnload method was also being called but that was not the case.
Related
I have problem with my collection view and reloading/inserting items. I have my items array in view controller which contains UICollectionView. I change content of items array in many places. Sometimes I insert new items and sometimes I must reload items again from database.
Not all the time but sometimes I get "classic" error when inserting new items:
Invalid update: invalid number of items in section 0. The number of
items contained in an existing section after the update (16) must be
equal to the number of items contained in that section before the
update (16), plus or minus the number of items inserted or deleted from
that section (1 inserted, 0 deleted) and plus or minus the number of
items moved into or out of that section (0 moved in, 0 moved out).
I know meaning of this error but It's really hard to fix this because as I wrote I can get notifications and then I reload data immediately (get items from database and reload collection view) and it could happen when inserting new item and similar conflicts could happen.
So I am not sure what is best solution for this. Should I lock array and make it thread safe (but I think I edit it mostly in main thread) or should I somehow "lock" collection and when there is insert operation then there couldn't be changes to items or collection view couldn't be reloaded? Or is there other solution?
Bonus: Is it possible that app wouldn't crash when error above happens and just full reload collection view? Propably not but it could help a lot.
My app has two CollectionViewControllers. Only one is visible at a given time.
I have created the following structure on storyboard: two container views on top of each other. Every container view has a CollectionViewController embedded. The visibility of a particular container view determines which collectionViewController is visible.
This is the problem. Both CollectionViewControllers are receiving data in parallel but iOS has a bug that will make the app crash if one CollectionViewController tries to execute an insert using performBatchUpdates while it is invisible.
Trying to prevent that, I have created a BOOL flag on both CollectionViewControllers so they can know if they are visible and execute or not the performBatchUpdates. Something like:
if (self.isThisCollectionViewVisible == NO) return;
[self.collectionView performBatchUpdates:^{
// bla bla... perform insert,m remove...
This solves part of the problem. But the app continues to crash on the following condition: if I tap the button to switch to the invisible CollectionViewController making it visible while it is receiving updates.
I mean this: lets call A the first CollectionViewController and B the second one. A is visible and B is invisible at this point. B starts receiving data and is trying to do a performBatchUpdates but as it is invisible, the if (self.isThisCollectionViewVisible == NO) return; is preventing performBatchUpdates to run, what is fine. Now I make A invisible and B visible. At this point the flag self.isThisCollectionViewVisible is set to YES and performBatchUpdates makes the app crash with this error:
* Assertion failure in -[CollectionView _endItemAnimationsWithInvalidationContext:tentativelyForReordering:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3512.60.7/UICollectionView.m:4625
* Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid
number of items in section 0. The number of items contained in an
existing section after the update (76) must be equal to the number of
items contained in that section before the update (70), plus or minus
the number of items inserted or deleted from that section (5 inserted,
2 deleted) and plus or minus the number of items moved into or out of
that section (0 moved in, 0 moved out).'
I think the CollectionViewController is really not yet ready and updated to be able to do a performBatchUpdates... and this is not a matter of not updating the data source previously because it is being updated.
What checks can I do to prevent that from happening?
NOTE: I noticed something strange about this crash in particular. It says that 5 elements are being inserted and 2 deleted but in fact 3 elements are being inserted, 0 deleted and 2 changed when the crashes happen.
For me adding self.collectionView.numberOfItemsInSection(0) fixed the crash.
The collectionView has issues while inserting items when it is not visible.
Seems like I'm not alone with my solution: http://www.openradar.me/15262692
This crash told you that you didn't updated your datasource for collection. You need to update your dataSource (array or dictionary) and reload collection view data after you perform performBatchUpdates.
Invalid update: invalid number of items in section 0. The number of items contained in an existing section after the update (76) must be equal to the number of items contained in that section before the update (70), plus or minus the number of items inserted or deleted from that section (5 inserted, 2 deleted) and plus or minus the number of items moved into or out of that section (0 moved in, 0 moved out).'
As written in apple docs
Deletes are processed before inserts in batch operations. This means
the indexes for the deletions are processed relative to the indexes of
the collection view’s state before the batch operation, and the
indexes for the insertions are processed relative to the indexes of
the state after all the deletions in the batch operation.
So, move the changes before the inserts and it will the trick!
Encountered the same error today, for me, in performBatchUpdates block replace this:
NSArray *selectedItemsIndexPaths = [self.collectionView indexPathsForSelectedItems];
with this:
NSIndexPath *selectedIndexPath = [NSIndexPath indexPathForRow:self.selectIndex inSection:0];
NSArray *selectedItemsIndexPaths = #[selectedIndexPath];
Maintain the index by myself, it's OK now. The error should not be associated with data source, if you have had update the data source. It maybe related to the reuse of cells.
I have an NSMutableArray _conversationsArray that basically stores IDs of all the conversations a user has in my app. Based on that value I show different number of rows in the tableView. When I delete a conversation from the data source and trigger reload of the tableView, numberOfRowsInSection method triggers and by setting a breakpoint I check the number of elements (conversations) in that array:
Everything seems to be fine, the result is one object which is great because I had two of them before the deletion. The problem is, as you can see on the far left of the screen, both rows are still visible in the tableView (even after the breakpoint) :/ The second row should have disappeared but it didn't. It did become unresponsive to touch events, but I need it gone.
Have you ever experienced a problem like this? Any help would be greatly appreciated.
--- Update ---
Could it be that it has to do something with the threads? because it seems that the table updates as it should when the thread changes :/ I might be wrong about it as it's hard to debug
It looks like you're not reloading the table view on the main thread, since -tableView:numberOfRowsInSection is called on a background thread (?). In UIKit -reloadData must be called on the main thread.
When dealing with a UICollectionView in my app I've ran into a strange problem related to reloading data. After lot's of debugging and analyzing logs I've come to the conclusion that if reloadData is immediately followed by insertItemsAtIndexPaths the dreaded error below is guaranteed to occur:
Name: NSInternalInconsistencyException Reason: Invalid update: invalid
number of items in section 0. The number of items contained in an
existing section after the update (1) must be equal to the number of
items contained in that section before the update (1), plus or minus
the number of items inserted or deleted from that section (1 inserted)
...
They only way for this to happen consistently is that internally the UICollectionView is still busy with reloadData when the call to insertItemsAtIndexPaths arrives. The fact that "collectionView:numberOfItemsInSection" is called twice in a row before the insertItemsAtIndexPaths completes seems to support this since that method is never called twice in a row in call other cases.
Has anyone seen similar behavior or can confirm my analysis or even suggest a proper workaround?
Update: Any yes I've made sure that all relevant invocations occur on the main thread.
Update 2: Since the reasoning behind getting into this situation at all has been questioned: I'm using Monotouch and the code in question is intended to keep generic .Net Collections firing this event into the appropriate calls to keep the UICollectionView bound to the collection in sync. When the source collection is cleared it reacts with a Reset action, followed by one or more Add actions when items get inserted into it which leads to the problem outlined above. Hope this helps.
When you call insertItemsAtIndexPaths (removeItemsAtIndexPaths is analogous), you are telling your collectionview that its datasource now has more items available, and that it should insert these available items at the indexpaths you specify.
It checks your datasource whether that statement is true, and if it detects that the amount of old items plus the amount of items you say you inserted is not equal to the amount of new items, it says it can't do the update, as you lied about how many items you changed.
Now, what you are doing is you are telling your collectionview is that it should reload all its data from its datasource (with the new data) and right after that, you tell it you inserted x items. That is a false statement, as you just reloaded the collectionview, which updated its amount of items, and thus the amount of items before the update is equal to the amount of items after the update (you're not doing anything), and not increased by the amount of indexpaths you specified.
I hope you're still with me, because here's your solution:
Remove the reloadData before the insertItemsAtIndexPaths, as this breaks its assertions and will throw exceptions when incorrectly used. If you would like to reload the collectionview before inserting items, make sure you perform insertItemsAtIndexPaths right after you change the items in the datasource.
Read up on the documentation for this method here.
I have a UITableView that is backed by core data with sections grouped by date. I can delete and add while I'm on the that view just fine. The NSFetchController and the UITableView stay in sync just fine. But then I drill down to an individual object, make changes, save and return. I don't add from the other view, but sometimes delete, most of the the time I'm just making edits to existing records, and none of the edits would cause them to change which section they belonged to. At that point if I try to delete a row I get:
Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-1448.89/UITableView.m:974
2011-10-01 14:55:42.691 Lotus Bud[8073:fa03] Serious application error. An exception was caught from the delegate of NSFetchedResultsController during a call to -controllerDidChangeContent:. Invalid update: invalid number of sections. The number of sections contained in the table view after the update (1) must be equal to the number of sections contained in the table view before the update (1), plus or minus the number of sections inserted or deleted (0 inserted, 1 deleted). with userInfo (null)
What do I need to do to get them back in sync after saving from another view.
I would suggest listening for the NSManagedObjectContextDidSaveNotification and breaking in the debugger when it is fired. Then you can see what section is being deleted and hopefully backtrace to the source of the problem.