In my app I have 2 detail view controllers:
product name update controller
product properties update controller
In product properties update view controller everything is fine there is nothing wrong.
In product name update view controller however saving the context does not give any error. I see that the product name change in root view controller but when I re-open my app the product name shows me the old name. So it is not persisted.
What is my problem according to my updateProduct method:
-(void)updateProduct:(id)sender
{
AppDelegate *delegate = [UIApplication sharedApplication].delegate;
NSManagedObjectContext *context = [delegate managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:#"Products" inManagedObjectContext:context]];
NSError *error = nil;
NSPredicate *predicateID =[NSPredicate predicateWithFormat:#"productID==%d",[secim intValue]];
[request setPredicate:predicateID];
NSArray *myobj=[context executeFetchRequest:request error:&error];
NSManagedObject *prod1=[myobj objectAtIndex:0];
[prod1 setValue:textProduct1.text forKey:#"productName"];
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}
[self.navigationController popToRootViewControllerAnimated:YES];
NSLog(#"Data saved");
}
In addition to #Mundi here you are doing the following
NSArray *myobj = [context executeFetchRequest:request error:&error];
NSManagedObject *prod1 = [myobj objectAtIndex:0];
but you are not checking against error and neither if myobj contains elements.
ALWAYS check for errors whereas there is the possibility to have them.
Check with a breakpoint if your updateProduct method is called. I suspect it is not.
In the light of the other discussion, make sure that
the managed object context is not nil
prod1 (the managed object) is not nil
You can do this with breakpoints in the debugger or with log statements.
Related
I have a method which allows the user to export a .csv file of all data in my Core Data model. I'm using the wonderful CHCSV Parser after performing a fetchRequest to fetch the stored results. Once the .csv has been created, it gets attached to an email and exported from the device. This all works fine, the issues come when I delete the data.
I am using a somewhat popular technique to delete my data (by popular I mean it has been recommended on lots of Stack Overflow answers I have came researched). I simply fetch all objects and delete them one by one.
// Create fetchRequest
NGLSAppDelegate *appDelegate = (NGLSAppDelegate *)[[UIApplication sharedApplication]delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"NGLS"
inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSError *error;
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
// Delete objects
for (Model *results in fetchedObjects) {
[context deleteObject:(id)results];
NSLog(#"NGLS objects deleted");
};
My model is simple and only has two entities, so I use the same code for the other Admin entity too. This is all fine, all objects are deleted, and I can confirm this by doing another fetchRequest which returns the object count for each entity - both have a count of zero. The problem occurs when I try to save data back to either entity after the delete has been executed.
The ViewController with the above code is an "Admin" control screen, where the user can login and also export the data. So when the user logs in, here is the code to save:
// Save login details
[_managedObjectAdmin setValue:user forKey:#"userLogin"];
[_managedObjectAdmin setValue:site forKey:#"siteLocation"];
NSError *error;
[[self.managedObjectAdmin managedObjectContext] save:&error];
I then perform the fetchRequest above and export all data when the "Export" button is pressed. After that is complete, when I try to login on the same ViewController, the output is:
2014-10-27 12:43:49.653 NGLS[19471:607] <NSManagedObject: 0x7a8c2460> (entity: Admin; id: 0x7a82e3e0 <x-coredata://3C9F3807-E314-439C-8B73-3D4459F85156/Admin/p30> ; data: <fault>)
If I navigate back to another ViewController (using my navigation controller), then go back to the "Admin" control screen and try to login again, I get this output:
2014-10-27 12:44:04.530 NGLS[19471:607] *** Terminating app due to uncaught exception 'NSObjectInaccessibleException', reason: 'CoreData could not fulfill a fault for '0x7a82e3e0 <x-coredata://3C9F3807-E314-439C-8B73-3D4459F85156/Admin/p30>''
(I can post the full log if requested).
I have tried many things in an attempt to resolve this issue. Core Data is complex and I dont quite understand what I need to do to fix this. I have tried to delete the persistentStore and create it again, and the same with the managedObjectContext but nothing I have tried has worked. I implemented a resetStore method in my AppDelegate to delete and rebuild the store as follows:
- (void)resetStores {
NSError *error;
NSURL *storeURL = [[_managedObjectContext persistentStoreCoordinator] URLForPersistentStore:[[[_managedObjectContext persistentStoreCoordinator] persistentStores] lastObject]];
// lock the current context
[_managedObjectContext lock];
[_managedObjectContext reset];//to drop pending changes
//delete the store from the current managedObjectContext
if ([[_managedObjectContext persistentStoreCoordinator] removePersistentStore:[[[_managedObjectContext persistentStoreCoordinator] persistentStores] lastObject] error:&error])
{
// remove the file containing the data
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error];
//recreate the store like in the appDelegate method
[[_managedObjectContext persistentStoreCoordinator] addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error];//recreates the persistent store
}
[_managedObjectContext unlock];
}
And also tried this method:
- (NSPersistentStoreCoordinator *)resetPersistentStore
{
NSError *error = nil;
if ([_persistentStoreCoordinator persistentStores] == nil)
return [self persistentStoreCoordinator];
_managedObjectContext = nil;
NSPersistentStore *store = [[_persistentStoreCoordinator persistentStores] lastObject];
if (![_persistentStoreCoordinator removePersistentStore:store error:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
// Delete file
if ([[NSFileManager defaultManager] fileExistsAtPath:store.URL.path]) {
if (![[NSFileManager defaultManager] removeItemAtPath:store.URL.path error:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
// Delete the reference to non-existing store
_persistentStoreCoordinator = nil;
NSPersistentStoreCoordinator *r = [self persistentStoreCoordinator];
return r;
}
But neither of these work. What I have found to work is after the export has completed, by closing and reopening the app everything works as normal again. I have tried to figure out what process occurs when closing/opening the app in regards to Core Data but I just don't know what to look for. I have researched many questions on Stack Overflow and tried all the solutions but nothing works for me. I really need some help on this, or else I'm going to have to force the user to quit the app after the export is done by a exit(0); command (because it's not getting submitted to the App Store, its for in-house employees) although I don't want that solution, surely there is a way I can just reset my database and continue to use the app without having to shut it down every time. Thanks in advance.
References:
Deleting all records from Core Data
Reset a Core Data persistent store
How do I delete all objects from my persistent store in Core Data
I have managed to solve the issue by simply refreshing the view. By calling my viewDidLoad method after the export is complete I create a new managedObject ready to use as normal, without leaving that ViewController or exiting the app altogether.
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib
// Create fetchRequest
NGLSAppDelegate *appDelegate = (NGLSAppDelegate *)[[UIApplication sharedApplication]delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Admin" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSError *error = nil;
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
// Fetch last object
Model *admin = [fetchedObjects lastObject];
// Populate login fields with last stored details
if (admin.userLogin == nil) {
//NSLog(#"Login empty");
} else {
self.usernameField.text = admin.userLogin;
self.siteLocationField.text = admin.siteLocation;
}
// Create new managed object using the Admin entity description
NSManagedObject *ManagedObjectAdmin;
ManagedObjectAdmin = [NSEntityDescription insertNewObjectForEntityForName:#"Admin"
inManagedObjectContext:context];
// Declare managed object
self.managedObjectAdmin = ManagedObjectAdmin;
// Save context
NSError *saveError = nil;
[context save:&saveError];
// ... more stuff
}
The solution was so simple all along. I will leave this question/answer up so other people can benefit from it if they find themselves in my situation. Thanks.
EDIT: Re-creating the managedObjectAdmin anywhere after the export works too, there is no specific need to call the viewDidLoad method. After the export has completed, I can simply create the new managedObject and save the context and continue using the app as normal, without having to navigate to another ViewController first or restarting the app.
I have some really mysterious behaviour with CoreData.
I'll add an Object. I save this object. I fetch the new results and reload the collection view (from which is display the objects). The new object shows up. Hoorah! Just as expected.
I do this a second time, but every time from now (unless the app is restarted) when re-fetching the data from my NSFetchedResultsController and reloading the collection view, the new object doesn't appear.
Equally, if I delete an object. First time, A-OK! The next time I do this, the app actually crashes with the following error:
(Aircraft is my NSManagedObject)
Terminating app due to uncaught exception 'NSObjectInaccessibleException', reason: 'CoreData could not fulfill a fault for '0xd0000000000c0000 <x-coredata://C418948D-90CD-40E9-A502-C4CAB0134419/Aircraft/p3>''
*** First throw call stack:
(0x18b79f09c 0x197ad5d78 0x18b4a77ac 0x18b4a6cac 0x18b4a6b00 0x100034438 0x18e6d8a44 0x18e6d6dc0 0x18e6d2e44 0x18e66ed78 0x18e26b0cc 0x18e265c94 0x18e265b4c 0x18e2653d4 0x18e265178 0x18e25ea30 0x18b75f7e0 0x18b75ca68 0x18b75cdf4 0x18b69db38 0x19106f830 0x18e6dc0e8 0x1000217dc 0x1980bfaa0)
libc++abi.dylib: terminating with uncaught exception of type _NSCoreDataException
Time for some code. I can't see any issues, but here it is. I won't spam you with everything, but if something rings any alarms, I can always add it on request.
Starting with the main view controller. This contains my collection view. Just as a note, it has two sections each fetching data from an individual NSFetchedResultsController. I am only seeing the issue with this specific one though. Fairly standard fetched results controller.
- (NSFetchedResultsController *)aircraftFetchedResultsController
{
if (_aircraftFetchedResultsController != nil) {
return _aircraftFetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Aircraft" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:50];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:YES];
NSArray *sortDescriptors = #[sortDescriptor];
[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:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Master"];
aFetchedResultsController.delegate = self;
self.aircraftFetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.aircraftFetchedResultsController 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.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return _aircraftFetchedResultsController;
}
Anywhere I use an NSManagedObjectContext I am getting it from my AppDelegate. When adding the new object, the user is in a modal (form sheet) view controller. I create a new object, but do not insert it immediately, incase the user cancels:
SLAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Aircraft" inManagedObjectContext:managedObjectContext];
self.aircraft = [[Aircraft alloc] initWithEntity:entity insertIntoManagedObjectContext:nil];
Then, when done, save the object:
SLAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
//Only need to insert the new object if its 'NEW' else just save the existing one we are editing
if (!isEditing)
{
//Create new aircraft
NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;
//We are definetly saving the object, so now we insert it
[managedObjectContext insertObject:self.aircraft];
}
//Save
[appDelegate saveContextWithCompletionBlock:^(BOOL didSaveSuccessfully) {
if (didSaveSuccessfully)
{
[self dismissViewControllerAnimated:YES completion:^{
[delegate addAircraftDidSave:YES];
}];
}
else
{
[self dismissViewControllerAnimated:YES completion:^{
//ALERT with error
}];
}
}];
I use a delegate to send a message back to the main view controller saying the object has saved. That method then fetches the new data and reloads the collection view to show the new object:
-(void)fetchAircraft
{
NSError *error;
if (![[self aircraftFetchedResultsController] performFetch:&error])
{
// Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
[UIAlertView showGenericErrorAlert];
}
//Success, we have results
else
{
[self.collectionView reloadData];
}
}
Done. As I said, this works first time, then start acting up. Equally, you can substitute the save code for the delete code I have, fairly similar, delete and save changes:
SLAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext;
[managedObjectContext deleteObject:self.aircraft];
[appDelegate saveContextWithCompletionBlock:^(BOOL didSaveSuccessfully) {
if (didSaveSuccessfully)
{
[self dismissViewControllerAnimated:YES completion:^{
[delegate addAircraftDidSave:YES];
}];
}
else
{
//ALERT with error
}
}];
(From my above comment:) The two fetched results controllers must use different
caches (cacheName: parameter). I also think (but I am not 100% sure about that)
that without sections, a cache does not give any advantages, so you can also
try cacheName:nil.
I believe you'll need to use separate ManagedObjectContexts for saves on a background thread.
https://developer.apple.com/library/ios/documentation/cocoa/conceptual/CoreData/Articles/cdConcurrency.html
I am trying to add objects to a Core Data Database using the following code:
NSManagedObjectContext *managedObjectContext = [[NSManagedObjectContext alloc] init];
managedObjectContext.persistentStoreCoordinator = [[CoreDataController sharedCoreDataController] persistentStoreCoordinator];
Feed *feed = [NSEntityDescription insertNewObjectForEntityForName:#"Feed" inManagedObjectContext:managedObjectContext];
feed.feedID = dictionary[#"feed_id"];
feed.siteURL = dictionary[#"site_url"];
feed.title = dictionary[#"title"];
NSError *error;
if (![managedObjectContext save:&error]) {
NSLog(#"Error, couldn't save: %#", [error localizedDescription]);
}
Feed is a subclass of NSManagedObject. The persistentStoreCoordinator returned from the sharedCoreDataController (a singleton) is the persistentStoreCoordinator from a UIManagedDocument (created or opened when the app launches). As far as I can tell, the document is being created or opened successfully. I am running this code in the simulator, and I'm looking in the directory in which I am saving the Database (the apps Documents directory), but the persistentStore file is not being updated to reflect the new objects being added. Am I doing something wrong? I should also point out that the above code is being executed multiple times on a concurrent, asynchronous queue.
Any help would be much appreciated, thanks in advance.
Update: After the suggestions from Alexander and Duncan, the code above has been updated to reflect the changes. Sadly, however, I haven't noticed any difference (the new data is not appearing in the persistentStore file).
Have you called the line to save your managedObjectContext? How about this:
NSError *error;
if (![managedObjectContext save:&error]) {
NSLog(#"Error, couldn't save: %#", [error localizedDescription]);
}
Try using something like this
NSManagedObjectContext *managedObjectContext = [[NSManagedObjectContext alloc] init];
managedObjectContext.persistentStoreCoordinator = [[CoreDataController sharedCoreDataController] persistentStoreCoordinator];
for (NSDictionary *dictionary in arrayOfData) {
Feed *feed = [NSEntityDescription insertNewObjectForEntityForName:#"Feed" inManagedObjectContext:managedObjectContext];
feed.feedID = dictionary[#"feed_id"];
feed.siteURL = dictionary[#"site_url"];
feed.title = dictionary[#"title"];
}
NSError *error;
if (![managedObjectContext save:&error]) {
NSLog(#"Error, couldn't save: %#", [error localizedDescription]);
}
I would avoid creating a managedObjectContext for each object you insert.
First, using UIManagedDocument is not recommended. It is not intended to be your single app wide context. It is meant for document style applications.
Second, the NSManagedObjectContext that is exposed from the UIManagedDocument doesn't have a NSPersistentStoreCoordinator attached to it. It is a child context of a private NSManagedObjectContext that then has a NSPersistentStoreCoordinator. I suspect that if you used the debugger you may find that your NSManagedObjectContext is missing its NSPersistentStoreCoordinator.
In any event, you are using UIManagedDocument and then trying to attach another NSManagedObjectContext to the same NSPersistentStoreCoordinator. That is a bad design and you should at a minimum remove the UIManagedDocument or stop creating a new NSManagedObjectContext.
What is the point of the new context? What are you trying to solve with this code?
Problem in short
Since NSManagedObjectContext without persistent store coordinator doesn't support setFetchBatchSize selector, I've used a solution from this post and it works with certain issue, that I would like to resolve.
Here is the database scheme and Coredata structure with terms in brackets. Test application has two screens: master table with list of Chats and detail table with list of Messages. Master screen uses Main MOC in fetch controller for showing data in table and Worker MOC to create Chats and Messages. Detail screen uses Fetch MOC for showing data in table.
After I create a new Chat with Messages on master screen and save them with calling save on all MOCs in the hierarchy, I can't fetch Messages by a selected Chat in detail screen. All I got in console is: "CoreData: annotation: total fetch execution time: 0.0000s for 0 rows". it is possible to fetch this data after app restart.
It seems it has something to do with fault Messages in Fetch MOC having fault relations with Chats that have different objectID than Chats I have in Main MOC. Because when I fetch Chat object in Fetch MOC and then use it for finding Messages, everything is working fine.
I would appreciate it if someone could help me resolve this issue with Fetch MOC or maybe it is just fine to screw with all Object Graph concept and fetch data by my own ID fields instead of using relations.
Some code
Here is Coredata stack initialization which is done on didFinishLaunchingWithOptions:
- (void)initializeCoreDataStack
{
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"FaultsFetching" withExtension:#"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:_managedObjectModel];
_writerMOC = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[_writerMOC setUndoManager:nil];
[_writerMOC setPersistentStoreCoordinator:_persistentStoreCoordinator];
_mainThreadMOC = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[_mainThreadMOC setUndoManager:nil];
[_mainThreadMOC setParentContext:_writerMOC];
_fetchMainThreadMOC = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
[_fetchMainThreadMOC setUndoManager:nil];
[_fetchMainThreadMOC setMergePolicy:NSMergeByPropertyStoreTrumpMergePolicy];
[_fetchMainThreadMOC setPersistentStoreCoordinator:_persistentStoreCoordinator];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(backgroundContextDidSave:) name:NSManagedObjectContextDidSaveNotification object:_writerMOC];
NSURL *storeURL = [APP_DOC_DIR URLByAppendingPathComponent:#"FaultsFetching.sqlite"];
NSError *error = nil;
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
{
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
- (void)backgroundContextDidSave:(NSNotification *)notification
{
[_fetchMainThreadMOC mergeChangesFromContextDidSaveNotification:notification];
NSLog(#"Yep, everything is merged");
}
Here is how I create Worker MOCs:
+ (NSManagedObjectContext *)createPrivateMOC
{
CoreDataManager *scope = [CoreDataManager sharedInstance];
NSManagedObjectContext *workerMOC = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
workerMOC.parentContext = scope.mainThreadMOC;
[workerMOC setUndoManager:nil];
workerMOC.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy;
return workerMOC;
}
Here is how Multi-Context save looks like. Argument async is YES. Naturally this selector is called within performBlock selector of a worker MOC
+ (void)writeToDiskAsync:(BOOL)async
{
CoreDataManager *scope = [CoreDataManager sharedInstance];
NSManagedObjectContext *writeManagedObjectContext = scope.writerMOC;
NSManagedObjectContext *mainManagedObjectContext = scope.mainThreadMOC;
PerformBlock mainMOCBlock = ^
{
NSError *mainError = nil;
if ([mainManagedObjectContext hasChanges] && ![mainManagedObjectContext save:&mainError])
{
ALog(#"Unresolved error %#, %#", mainError, [mainError userInfo]);
}
PerformBlock writerBlock = ^
{
NSError *writeError = nil;
if ([writeManagedObjectContext hasChanges] && ![writeManagedObjectContext save:&writeError])
{
ALog(#"Unresolved error %#, %#", writeError, [writeError userInfo]);
}
NSLog(#"Yep, everything is saved");
};
[scope performBlock:writerBlock onMOC:writeManagedObjectContext async:async];
};
[scope performBlock:mainMOCBlock onMOC:mainManagedObjectContext async:async];
}
- (void)performBlock:(PerformBlock)block onMOC:(NSManagedObjectContext *)target async:(BOOL)async
{
if (async)
[target performBlock:block];
else
[target performBlockAndWait:block];
}
Here is my fetch results controller on detail screen, where "detailItem" is a Chat entity set from master screen and "[CoreDataManager sharedInstance]" is a singleton:
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
if (self.detailItem == nil)
return nil;
NSManagedObjectContext *fetchMOC = [CoreDataManager sharedInstance].fetchMainThreadMOC;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Messages" inManagedObjectContext:fetchMOC];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"sentDate" ascending:NO];
[fetchRequest setSortDescriptors:#[sortDescriptor]];
NSPredicate *chatPredicate = [NSPredicate predicateWithFormat:#"relatedChat=%#", self.detailItem.objectID];
[fetchRequest setPredicate:chatPredicate];
_fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:fetchMOC sectionNameKeyPath:#"sectionIdentifier" cacheName:nil];
_fetchedResultsController.delegate = self;
NSError *error = nil;
if (![_fetchedResultsController performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}
A bit of background
Parent/child MOCs were used to improve stability and responsiveness in the app that wasn't properly written from the beginning. However, because now everything related to Coredata is more or less centralized, it is possible to change the stack to something different.
SectionIdentifier is used for grouping messages by day like this: http://i.imgur.com/17tuKS7.png
Something else I might add later, also sorry for links and images: reputation and silly stuff
This is due to a bug. The workaround is to call obtainPermanentIDsForObjects: before saving the newly inserted objects.
See the following SO issue for more details:
Core Data: Do child contexts ever get permanent objectIDs for newly inserted objects?
So I have a utility app and I am trying to save some text into a "To" and "Message: text field on the Flipside View Controller. However, my data won't save. I am new to objective C and I have been using multiple different tutorials to the point where I have totally confused myself. Hopefully you can help me out. Not sure what else to do at this point...
FlipsideViewController.m
#import "CCCFlipsideViewController.h"
#import "CCCAppDelegate.h"
#import "CCCMainViewController.h"
#import "MessageDetails.h"
#interface CCCFlipsideViewController ()
{
// NSManagedObjectContext *context;
}
#end
#implementation CCCFlipsideViewController
#synthesize allMessageDetails;
#synthesize managedObjectContext;
- (void)awakeFromNib
{
[super awakeFromNib];
CCCAppDelegate *appDelegateController = [[CCCAppDelegate alloc]init];
self.managedObjectContext = appDelegateController.managedObjectContext;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:#"MessageDetails" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
NSError *error;
self.allMessageDetails = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
/*
NSManagedObject *managedObject; = [_fetchedResultsController valueForKey:#"to"];
self.toTextField.text = managedObject to;
messageDetails.to = [allMessageDetails firstObject];
self.toTextField.text = messageDetails.to;
messageDetails.message = [allMessageDetails valueForKey:#"message"];
self.messageTextField.text = messageDetails.message;
*/
NSLog(#"The 'to' is currently at %# after viewdidload", self.toTextField.text);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
return [textField resignFirstResponder]; //function says that if (bool) the text field is open and the keyboard hits return, text field is to resign first responder.
}
#pragma mark - Actions
- (IBAction)done:(id)sender
{
[self.delegate flipsideViewControllerDidFinish:self];
}
- (IBAction)resignFirstResponder:(id)sender {
[self.toTextField resignFirstResponder];
[self.messageTextField resignFirstResponder];
NSLog(#"Resigned First Responder");
}
- (IBAction)save:(id)sender {
// Create a new instance of the entity managed by the fetched results controller.
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];
// If appropriate, configure the new managed object.
[newManagedObject setValue:self.toTextField.text forKey:#"to"];
[newManagedObject setValue:self.messageTextField.text forKey:#"message"];
// Save the context.
NSError *error = nil;
if (![context save:&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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
*/
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
#pragma mark -
#pragma mark Fetched results controller
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
/*
Set up the fetched results controller.
*/
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"MessageDetails" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"to" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, 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:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Root"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![_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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
*/
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}
#end
I didn't look at all your code because there was a problem near the top that negates everything you do thereafter. Don't alloc/init your app delegate in awakeFromNib or anywhere else for that matter. The one and only instance of your app delegate already exists (I have no idea what happens when there is more than one app delegate).
CCCFlipsideViewController needs to gain access to the managed object context through another means. Perhaps CCCMainViewController (or another view controller) could set the CCCFlipsideViewController's managedObjectContext property. If CCCMainViewController does not have access to the managed object context, have the app delegate pass that context to it.
Example:
App delegate sets a managedObjectContext property on the root view controller; the root view controller, in turn, sets the managedObjectContext property on a child view controller (like your flipside VC), etc.
You don't seem to ever actually set self.messageTextField.text or self.toTextField.text to anything -- you have commented out code in your viewDidLoad method which sets these fields. bilobatum is entirely correct about your AppDelegate issue as well -- you could also use something like
[((NSObject*)[UIApplication sharedApplication].delegate) valueForKey: #"managedObjectContext"];
to get the app delegate for your application if you want to fix that fast, though long term bilobatum's solution to this is better design.
Honestly, I think you've done quite a number on this code... ;)
OK, first off, in your save method, don't create another NSManagedObjectContext, use the instance variable you already declared, "managedObjectContext."
Secondly, I think you've made things way too complicated for yourself... Storing Core Data is actually shockingly simple once you've created the NSManagedObject subclasses and set up everything in the App Delegate...
It seems as if you wouldn't need any info from the "fetchedResultsController" at that point in your code, since you're saving, not fetching. Maybe try changing your save method to something like:
- (IBAction)save:(id)sender {
NSEntityDescription *entity = [NSEntityDescription insertNewObjectForEntityForName:#"MessageDetails" inManagedObjectContext:self.managedObjectContext];
// If appropriate, configure the new managed object.
[entity setValue:self.toTextField.text forKey:#"to"];
[entity setValue:self.messageTextField.text forKey:#"message"];
// Save the context.
NSError *error = nil;
[self.managedObjectContext save:&error]
if (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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
*/
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
Edit: And to get the managed object context from the app delegate...
Right after your #synthesize's, create a variable for the App Delegate.
AppDelegate* appDelegateController;
And in viewDidLoad, initialize it:
appDelegateController = (AppDelegate*)[[UIApplication sharedApplication] delegate];
Right after viewDidLoad (or anywhere you want), you can stick in a method to declare the managed object context:
- (NSManagedObjectContext*)managedObjectContext {
return appDelegateController.managedObjectContext;
}
Then back in viewDidLoad, call that method with:
self.managedObjectContext = [self managedObjectContext];