I have a problem, storing instances of a viewController object. I want every user to have his/her own screen with some info on it and then be able to do modal to switch user.
The class instance of "User" and the array "Users" are defined in the .h file and the loop runs 5 times - but the array never gets populated:
- (void) chooseNumberOfUsers:(id)sender {
numberOfUsers = [sender tag];
NSLog(#"Number of users: %i", numberOfUsers);
currentUser = 0; // Nul-indekseret
// Herefter skal vi oprette spillerobjekter
users = [[NSMutableArray alloc] init];
for (int i=0; i<numberOfUsers; i++) {
user = [[UserViewController alloc] init];
user.userid = i+1;
[users addObject:user];
}
[users addObject:nil]; // Is this necessary?
// Debug: show info about the first user
NSLog(#"%#", [users objectAtIndex:0]); }
The user-object are created, but as mentioned, the array "users" never gets populated.
When it has run 5 times, it throws this error:
Terminating app due to uncaught exception
'NSInvalidArgumentException', reason: '* -[__NSArrayM
insertObject:atIndex:]: object cannot be nil'
The following line is causing the error
[users addObject:nil]; // Is this necessary?
As the exception states, you can't add nil to a NSArray. If you ever need to add a null value to a Cocoa collection, NSNull is the way to do it.
Related
I have an NSOperationQueue that has some NSBlockOperations added to it, among which are blockOperations A and B. The NSOperationQueue has a maxConcurrencyOperationCount of 1.
blockOperation B, is dependant on A being finished. In each of the blockOperations I am calling a method, which in turn calls another method, that initialises a new NSManagedObjectContext (with the persistentStoreCoordinator from a singleton), that I use to create and add objects to a Core Data database. The code invoked by the aforementioned second method call in A and B looks like this (it varies slightly for for each of them):
NSManagedObjectContext *managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
managedObjectContext.persistentStoreCoordinator = [[CoreDataController sharedCoreDataController] persistantStoreCoordinator];
for (NSDictionary *articleDictionary in array) {
if (![Article articleExistsWithIDInDictionary:articleDictionary inContext:managedObjectContext]) {
[Article articleFromDictionary:articleDictionary inContext:managedObjectContext];
}
}
[[CoreDataController sharedCoreDataController] saveContext:managedObjectContext];
// method ends.
The saveContext: code looks like this:
NSError *error = nil;
if (managedObjectContext != nil) {
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
}
}
Having spent a lot of time reading Apples Docs about Core Data Concurrency, NSOperation, etc., I'm still unsure if what I'm doing with NSManagedObjectContext is thread-safe, and generally considered to be OK? Some clarification and/or indication of that I should be doing differently would be much appreciated. If you need to see any more code, please ask.
Thanks in advance.
What you are doing is NOT thread safe.
If you decide to create a context per operation, you better use the confinement concurrency type:
context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
this way you don't need to change anything in your current code.
if you want to use the context with NSPrivateQueueConcurrencyType you must access objects within that context by the performBlock: or performBlockAndWait::
[managedObjectContext performBlockAndWait:^{//wait is used as to not end the operation before this code is executed
for (NSDictionary *articleDictionary in array) {
if (![Article articleExistsWithIDInDictionary:articleDictionary
inContext:managedObjectContext])
{
[Article articleFromDictionary:articleDictionary
inContext:managedObjectContext];
}
}
}];
I would probably go with my first solution in your case.
all that said, you could simply use a "private queue" context as a serial queue (as long as you add block operation to it in the order you need them to execute).
A context performBlock: method will queue the block and execute it serially in regard to other blocks added that context for execution in the background:
//add this to your CoreDataController
context = [[CoreDataController sharedCoreDataController] serialExecutionBGContext];
[context performBlock:^{ //your block operation code1}];
[context performBlock:^{ //your block operation code2}];
this will perform code1 and code2 in the background serially.
In this manner, you save the overhead of allocating a new context, and might benefit from caching done by this context.
You might want to reset this context every now and then so it will not get bloated with fetched objects.
The concern with the context is that it be accessed only within a single thread. Setting the MaxConcurrencyOperationCount does not guarantee that. Another approach is to make the context a "thread" variable, storing a context in each thread dictionary where it is used.
Ex:
+ (NSManagedObjectContext*)managedObjectContext
{
NSMutableDictionary *threadDictionary = [[NSThread currentThread] threadDictionary];
NSManagedObjectContext *context = [threadDictionary valueForKey:#"QpyManagedObjectContext"];
if (context == nil) {
#autoreleasepool {
context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
[context setStalenessInterval: 10.0];
[context setMergePolicy:[[NSMergePolicy alloc]initWithMergeType:NSOverwriteMergePolicyType]];
NSPersistentStoreCoordinator *coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[Qpyd managedObjectModel]];
[context setPersistentStoreCoordinator:coordinator];
NSString *STORE_TYPE = NSSQLiteStoreType;
NSString *path = [[NSProcessInfo processInfo] arguments][0];
path = [path stringByDeletingPathExtension];
NSURL *url = [NSURL fileURLWithPath:[path stringByAppendingPathExtension:#"sqlite"]];
NSError *error;
NSPersistentStore *newStore = [coordinator addPersistentStoreWithType:STORE_TYPE configuration:nil URL:url options:nil error:&error];
if (newStore == nil) {
NSLog(#"Store Configuration Failure %#", ([error localizedDescription] != nil) ? [error localizedDescription] : #"Unknown Error");
}
[threadDictionary setObject:context forKey:#"QpyManagedObjectContext"];
}
}
return context;
}
I am trying to save a one-to-many relation in core data. There is a user decision involved to determine whether the new child list object needs to be attached to a new parent object. In the other case an existing database entry is used as a parent object. Under certain circumstances after saving, the app crashes.
FINAL EDIT: Sorry if you mind me keeping all of the edits, I still will. The process of enlightenment was quite convoluted. After all I started out thinking it was a data conflict... Thanks again to Tom, who helped point me in the right direction: I am still using a relation for sorting and grouping core data entities with an NSFetchedResultsController. I have written a valid compare: method for my entity class now and so far from what I can see it is working. I am about to write an answer for my question. I will still be very grateful for any information or warnings from you concerning this!
EDIT 3: The save procedure and the user alert seem to be incidental to the problem. I have zoomed in on the NSFetchedResultsController now and on the fact that I am using a relation ('examination') as sectionNameKeyPath. I will now try to write a compare: method in a category to my Examination entity class. If that does not work either, I will have to write a comparable value into my Image entity class in addition to the relation and use that for sections. Are y'all agreed?
EDIT 1: The crash only occurs after the user has been asked whether she wants a new examination and has answered YES. The same method is also entered when there was no user prompt (when the creation of a new examination has been decided by facts (no examination existing = YES, existing examination not timed-out = NO). In these cases the error does NOT occur. It must be that the view finishes loading while the alert view is open and then the collection view and its NSFetchedResultsController join the fun.
EDIT 2: Thanks to Tom, here is the call stack. I did not think it was relevant, but the view controller displays images in a collection view with sections of images per examination descending. So both the section key and the sort descriptor of the NSFetchedResultsController are using the examination after the MOCs change notification is sent. It is not the save that crashes my app: it is the NSSortDescriptor (or, to be fair, my way to use all of this).
The code for the NSFetchedResultsController:
#pragma mark - NSFetchedResultsController
- (NSFetchedResultsController *)fetchedResultsController
{
if (m_fetchedResultsController != nil) {
return m_fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:NSStringFromClass([Image class]) inManagedObjectContext:[[HLSModelManager currentModelManager] managedObjectContext]];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Edit the sort key, identical sort to section key path must be first criterion
NSSortDescriptor *examinationSortDescriptor = [[NSSortDescriptor alloc] initWithKey:kexaminationSortDescriptor ascending:NO];
NSSortDescriptor *editDateSortDescriptor = [[NSSortDescriptor alloc] initWithKey:keditDateSortDescriptor ascending:NO];
NSArray *sortDescriptors =[[NSArray alloc] initWithObjects:examinationSortDescriptor, editDateSortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:[[HLSModelManager currentModelManager] managedObjectContext] sectionNameKeyPath:kSectionNameKeyPath cacheName:NSStringFromClass([Image class])];
aFetchedResultsController.delegate = self;
m_fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
HLSLoggerFatal(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return m_fetchedResultsController;
}
#pragma mark - NSFetchedResultsControllerDelegate - optional
/* Asks the delegate to return the corresponding section index entry for a given section name. Does not enable NSFetchedResultsController change tracking.
If this method isn't implemented by the delegate, the default implementation returns the capitalized first letter of the section name (seee NSFetchedResultsController sectionIndexTitleForSectionName:)
Only needed if a section index is used.
*/
- (NSString *)controller:(NSFetchedResultsController *)controller sectionIndexTitleForSectionName:(NSString *)sectionName
{
return sectionName;
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
// In the simplest, most efficient, case, reload the table view.
[[self collectionView] reloadData];
}
/* THE OTHER DELEGATE METHODS ARE ONLY FOR UITableView! */
The code for saving examination (existing or new) and the new image:
-(BOOL)saveNewImage
{
BOOL done = NO;
// remove observer for notification after alert
[[NSNotificationCenter defaultCenter] removeObserver:self name:kExaminationTimedoutAlertDone object:nil];
Examination * currentExamination = [self getCurrentExamination];
if ([self userWantsNewExamination] == YES)
{ // if an examination was found
if (currentExamination != nil)
{ // if the found examination is not closed yet
if ([currentExamination endDate] == nil)
{ // close examination & save!
[currentExamination closeExamination];
NSError *savingError = nil;
[HLSModelManager saveCurrentModelContext:(&savingError)];
if (savingError != nil)
{
HLSLoggerFatal(#"Failed to save old, closed examination: %#, %#", savingError, [savingError userInfo]);
return NO;
}
}
}
currentExamination = nil;
}
// the examination to be saved, either new or old
Examination * theExamination = nil;
// now, whether user wants new examination or no current examination was found - new examination will be created
if (currentExamination == nil)
{
// create new examination
theExamination = [Examination insert];
if (theExamination == nil)
{
HLSLoggerFatal(#"Failed to create new examination object.");
currentExamination = nil;
return NO;
}
// set new examinations data
[theExamination setStartDate: [NSDate date]];
}
else
{
theExamination = currentExamination;
}
if (theExamination == nil)
{ // no image without examination!
HLSLoggerFatal(#"No valid examination object.");
return NO;
}
Image *newImage = [Image insert];
if (newImage != nil)
{
// get users last name from app delegate
AppDelegate * myAppDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
// set image data
[newImage setEditUser: [[myAppDelegate user] lastName]];
[newImage setEditDate: [NSDate date]];
[newImage setExamination: theExamination];
[newImage setImage: [self stillImage]];
[newImage createImageThumbnail];
// update edit data
[theExamination setEditUser: [[myAppDelegate user] lastName]];
[theExamination setEditDate: [NSDate date]];
// unnecessary! CoreData does it automatically! [theExamination addImagesObject:newImage];
//! Important: save all changes in one go!
NSError *savingError = nil;
[HLSModelManager saveCurrentModelContext:(&savingError)];
if (savingError != nil)
{
HLSLoggerFatal(#"Failed to save new image + the examination: %#, %#", savingError, [savingError userInfo]);
}
else
{
// reload data into table view
[[self collectionView] reloadData];
return YES;
}
}
else
{
HLSLoggerFatal(#"Failed to create new image object.");
return NO;
}
return done;
}
The error:
2013-05-22 17:03:48.803 MyApp[11410:907] -[Examination compare:]: unrecognized selector sent to instance 0x1e5e73b0
2013-05-22 17:03:48.809 MyApp[11410:907] CoreData: error: Serious application error. Exception was caught during Core Data change processing. This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification. -[Examination compare:]: unrecognized selector sent to instance 0x1e5e73b0 with userInfo (null)
2013-05-22 17:03:48.828 MyApp[11410:907] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Examination compare:]: unrecognized selector sent to instance 0x1e5e73b0'
And here are the entity class files, too:
//
// Examination.h
// MyApp
//
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
#class Image;
#interface Examination : NSManagedObject
#property (nonatomic, retain) NSDate * editDate;
#property (nonatomic, retain) NSString * editUser;
#property (nonatomic, retain) NSDate * endDate;
#property (nonatomic, retain) NSDate * startDate;
#property (nonatomic, retain) NSSet *images;
#end
#interface Examination (CoreDataGeneratedAccessors)
- (void)addImagesObject:(Image *)value;
- (void)removeImagesObject:(Image *)value;
- (void)addImages:(NSSet *)values;
- (void)removeImages:(NSSet *)values;
#end
//
// Examination.m
// MyApp
//
#import "Examination.h"
#import "Image.h"
#implementation Examination
#dynamic editDate;
#dynamic editUser;
#dynamic endDate;
#dynamic startDate;
#dynamic images;
#end
This error had nothing to do with the saving of data to the MOC.
Because the saving of the new image data is triggered in the prepareForSegue of the previous view controller and the user alert gives the next view controller the time to finish loading, also creating the NSFetchedResultsController and its connection to its delegate, the exception was raised in the temporary context of the save to the MOC and only after the user alert.
The NSFetchedResultsController had started listening for changes of the MOC only in this case. It seems that if it gets alerted to an MOC change it will fetch only the changes and only then it needs to compare the new data with the existing data. Further information on this would be very welcome!
Then, because I had set a sort descriptor (and also the sectionNameKeyPath) to a relation and not provided the means to sort the entity objects in my core data entity class, the NSFetchedResultsController could not continue. Looking back it seems all so easy and natural, I really become suspicious of the simplicity of my solution...
I find it interesting that it could fetch the initial data in one go, when no change interfered. After all it was using the same NSSortDescriptor. Any ideas?
This is my solution:
//
// MyCategoryExamination.m
// MyApp
//
#import "MyCategoryExamination.h"
#implementation Examination (MyCategoryExamination)
- (NSComparisonResult)compare:(Examination *)anotherExamination;
{
return [[self startDate] compare:[anotherExamination startDate]];
}
#end
Please tell me if there is something wrong with this.
I need to use some core data managed objects in an NSOperation. The problem is that core data is not thread safe and apparently the object can't be loaded from the new thread. Does anybody know a good tutorial for this? I need the object read only... so the thread will not modify them in any way. Some other, unrelated entities may be added on the main thread while these objects are used in the background, but the background entities don't need to be modified at all..
Hmm seemed I fixed the background running issue, but now the problem is nothing is returned to the delegate... Why? In the thred if I nslog the results are all shown but that call to the delegate never happens
This is the code:
-(void)evaluateFormula:(Formula *)frm runNo:(NSUInteger)runCount{
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[queue setMaxConcurrentOperationCount:2];
NSManagedObjectID *formulaId = frm.objectID;
for (int i = 0; i < runCount; i++) {
NSInvocationOperation * op = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(runFormula:) object:formulaId];
[queue addOperation:op];
}
}
-(void)runFormula:(NSManagedObjectID *)fId {
NSManagedObjectContext *thredContext =[[NSManagedObjectContext alloc] init];
NSPersistentStoreCoordinator *coord = (NSPersistentStoreCoordinator *)[(PSAppDelegate *)[[UIApplication sharedApplication] delegate] persistentStoreCoordinator];
[thredContext setPersistentStoreCoordinator:coord];
Formula *f = (Formula *)[thredContext objectWithID:fId];
NSDictionary *vars = [self evaluateVariables:[f.hasVariables allObjects]];
NSMutableString *formula = [NSMutableString stringWithString:f.formula];
for (NSString *var in [vars allKeys]) {
NSNumber *value =[vars objectForKey:var];
[formula replaceOccurrencesOfString:var withString:[value stringValue] options:NSCaseInsensitiveSearch range:NSMakeRange(0, [formula length])];
}
//parse formula
NSNumber *result = [formula numberByEvaluatingString];
// NSLog(#" formula %# result : %d",formula,[result intValue]);
//aggregate results
[self performSelectorOnMainThread:#selector(aggregate:) withObject:result waitUntilDone:YES]; // the delegate doesn't get called ...
}
-(void)aggregate:(NSNumber *)res {
[self.delegate didReceiveResult:res];
}
I've read a lot of similar posts but after two days, I thought I should ask my own question.
I have a separate CoreData Controller. This passes the entity object fine from AppDelegate to the RootViewController. It does not pass it to a specific (Category) view controller, and I cant figure out why.
The code in App Delegate where I try to pass the object is this:
rootViewController.managedObjectContext = self.coreDataController.mainThreadContext;
categoryListViewController.managedObjectContext = self.coreDataController.mainThreadContext;
NSLog(#"AD/core data controller is %#", coreDataController.mainThreadContext);
NSLog(#"AD- rootVC is %#", rootViewController.managedObjectContext);
NSLog(#"AD/category list is %#", categoryListViewController.managedObjectContext);
and the logs show that the core data controller and the root vc get populated, but the Category vc doesn't.
2012-12-02 14:28:33.187 [50351:907] AD/coredatacontroller moc is <NSManagedObjectContext: 0x21065160>
2012-12-02 14:28:33.188 [50351:907] AD/categorycontroller moc is (null)
2012-12-02 14:28:33.190 [50351:907] AD- rootVC moc is <NSManagedObjectContext: 0x21065160>
Any ideas why?
UPDATE
If I do as suggested by Valentin, and init the Category VC in the App Delegate, I certainly get the managed objects passed through, however, as I call the view from the Detail VC. When I do that, I get the error "Application tried to push a nil view controller on target ".
If I try to init the category VC (and load the context) in the detail VC, it does not convey, and the logs show the context to be nil.
Init the VC (in App Delegate):
categoryListViewController = [[CategoryListViewController alloc] initWithNibName:#"CategoryList-iPad" bundle:nil];
// we have loaded from our xib, so has our CoreDataController,
// so connect as its delegate and setup its persistent store
//
self.coreDataController.delegate = self;
[self.coreDataController loadPersistentStores];
UINavigationController *rootNavigationController = [[UINavigationController alloc] initWithRootViewController:rootViewController];
UINavigationController *detailNavigationController = [[UINavigationController alloc] initWithRootViewController:detailViewController];
// Set up MASTER and DETAIL delegation so we can send messages between views
rootViewController.detailViewController = detailViewController;
detailViewController.rootViewController = rootViewController;
splitViewController = [[UISplitViewController alloc] init];
splitViewController.viewControllers = #[rootNavigationController, detailNavigationController];
[[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
splitViewController.delegate = detailViewController;
rootViewController.managedObjectContext = self.coreDataController.mainThreadContext;
categoryListViewController.managedObjectContext = self.coreDataController.mainThreadContext;
NSLog(#"AD - coreDataController is %#", coreDataController.mainThreadContext);
NSLog(#"AD - rootViewController is %#", rootViewController.managedObjectContext);
NSLog(#"AD - categoryListVC is %#", categoryListViewController.managedObjectContext);
Call the view (in DetailViewController):
-(void)categoryButtonTapped {
NSLog(#"%s", __FUNCTION__);
//categoryListViewController = [[CategoryListViewController alloc] initWithNibName:#"CategoryList-iPad" bundle:nil];
//categoryListViewController.managedObjectContext = coreDataController.mainThreadContext;
//categoryListViewController.managedObjectContext = self.coreDataController.mainThreadContext;
UINavigationController *nc = [[UINavigationController alloc] initWithRootViewController:categoryListViewController];
nc.modalPresentationStyle = UIModalPresentationFormSheet;
NSLog(#"DVC FRC is %#", self);
NSLog(#"DVC FRC/moc is %#", coreDataController.mainThreadContext);
NSLog(#"DVC FRC/self.moc is %#", self.coreDataController.mainThreadContext);
[self presentViewController:nc animated:YES completion:nil];
//[self.navigationController pushViewController:categoryListViewController animated:YES];
}
Most probably your categoryListViewController is nil as well. Try to see if it gets alloc'ed/initialised correctly.
I am trying to get my head around the core data and I am trying to implement a small to-many relationship but I keep getting the error below:
I have two NSManagedObject classes (Groups and Contacts) created by Xcode's data model with a to-many relationship.
#implementation Groups
#dynamic groupId;
#dynamic groupName;
#dynamic groupContacts;
#end
#implementation Contacts
#dynamic firstName;
#dynamic lastName;
#dynamic userId;
#dynamic belongsToGroup;
I have contacts data as an array of dictionaries and I am doing the following:
self.localGroup = [NSEntityDescription insertNewObjectForEntityForName:#"Groups" inManagedObjectContext:self.scratchPadContext];
self.localGroup.groupName = #"Some Name";
for (int i = 0; i < [self.ContactsData count]; i++) {
Contacts *contact = [NSEntityDescription insertNewObjectForEntityForName:#"Contacts" inManagedObjectContext:self.scratchPadContext];
NSDictionary *obj = (NSDictionary *)[self.ContactsData objectAtIndex:i];
contact.firstName = [obj valueForKey:#"firstName"];
contact.userId = [obj valueForKey:#"email"];
[self.localGroup addGroupContactsObject:contact];
}
if (![self.scratchPadContext save:&error]) {
NSLog(#"Errror saving Group ********************************* %#, %#", error, [error userInfo]);
}
I get the following Error:
[4459:15503] Errror saving Group *****************
Error Domain=NSCocoaErrorDomain Code=134030 "The operation couldn’t be
completed. (Cocoa error 134030.)" UserInfo=0x85e0ab0
{NSAffectedObjectsErrorKey=(
" (entity: Groups; id: 0x838d020 ; data:
{\n groupContacts = nil;\n groupId = 0;\n groupName = Some
Name;\n})" ), NSUnderlyingException=Cannot update object that was
never inserted.}, {
NSAffectedObjectsErrorKey = (
" (entity: Groups; id: 0x838d020 ; data:
{\n groupContacts = nil;\n groupId = 0;\n groupName = Some
Name;\n})"
);
NSUnderlyingException = "Cannot update object that was never inserted."; }
If I comment out the relationship part and just save the group name, it works fine. So, I guess the problem is with the relationship data but I cannot figure out what. Can anyone please point me to where I could be doing it wrong?
[EDIT]:
When I add
contact.belongsToGroup = self.localGroup;
I get the following error even though I am using one MOC. I cannot understand where the mistake is. I would greatly appreciate if anyone can shed some light on this.
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Illegal attempt to establish a relationship 'belongsToGroup' between objects in different contexts (source = <Contacts: 0x86926a0> (entity: Contacts; id: 0x8692700 <x-coredata:///Contacts/t2548922E-A0C6-4E3C-9760-3265954764E73> ;
Have you tried saving the scratchPadContext before adding the contacts to the group (that is, creating the localGroup object, saving the context, then adding the contacts, and saving the context again? From the error message, it looks like Core Data is sending an update statement to the permanent store before it sends the necessary insert, so it may be getting tripped up because you're writing both ends of a new to-many relationship to the permanent store at the same time.