I'm trying to write an application with Core Data, and I have been able to successfully read and write to the core data database. However, if I write to the database in one view controller, my other view controllers will not see the change until the app is closed then reopened again. This is really frustrating. I'm not entirely sure how to get the refresh - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag method to work. How do I get a reference to my managed object?
Anyways, here's the code I'm using to read the data back. This is in the viewDidLoad method.
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Website" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"siteName" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if(mutableFetchResults == nil) {
//Handle the error
}
[self setNewsTitlesArray:mutableFetchResults];
[mutableFetchResults release];
[request release];
[newsSourcesTableView reloadData];
Thanks for help in advance!
I am not entirely sure what do you intend to do from what I understand you are changing your managed object context in one view controller and you want the result to be visible in other view controllers is this correct?. Anyway a solution for this is to listen for the NSManagedObjectContextDidSaveNotification (which is send when the context is saved) and register as a observer the view controller you want to be afected by the changes:
NSNotificationCenter *dnc = [NSNotificationCenter defaultCenter];
[dnc addObserver:myController selector:#selector(updateTable:) name:NSManagedObjectContextDidSaveNotification object:controller.context];
The updateTable in the myController Controller the selector could look something like this:
- (void)updateTable:(NSNotification *)saveNotification
{
if (fetchedResultsController == nil)
{
NSError *error;
if (![[self fetchedResultsController] performFetch:&error]) {
//Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
}
else
{
NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
// Merging changes causes the fetched results controller to update its results
[context mergeChangesFromContextDidSaveNotification:saveNotification];
[self.tableView reloadData];
}
Hope that helps.
-Oscar
Actually, what I found was that I had the table set to load as my view. When I put the table into another view, everything worked fine.
Related
I have 2 viewcontrollers (say A & B) ... I have some records in A now I want to edit the data in the core data.... For that I push the navigation controller to B.. There I edit the data in core data.. Itz working fine.. This the code I use for editing..
NSManagedObjectContext *managedContext = [self managedObjectContext];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"CamImage" inManagedObjectContext:managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
// Set the predicate -- much like a WHERE statement in a SQL database
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"name == %#", xapp.patientName];
[request setPredicate:predicate];
// Set the sorting -- mandatory, even if you're fetching a single record/object
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
sortDescriptors = nil;
NSError *error;
// Request the data -- NOTE, this assumes only one match, that
// yourIdentifyingQualifier is unique. It just grabs the first object in the array.
CamImage *event = [[managedObjectContext executeFetchRequest:request error:&error] objectAtIndex:0];
[event setMedicineImage:butImage];
[event setMedicineName:text.text];
[event setQuantity:[jst objectAtIndex:0]];
[event setUnit:[jst objectAtIndex:1]];
[event setMeal:meal];
request = nil;
NSMutableArray *mutableFetchResults = [[self.managedObjectContext executeFetchRequest:request1
error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
}
// Set self's events array to the mutable array, then clean up.
[self setCamImage:mutableFetchResults];
NSLog(#"AddMedicineArray:%#",camImage);
[self.navigationController popViewControllerAnimated:YES];
}
In above code I edited the data and fetched it once again..I can found the data got edited properly.. After editing I pop to B.. In the viewwillappear method I once again fetch the data.. But I find the old records only... Once I run the app again I found the edited data got fetched properly.. Here is the code in viewwillappear
-(void)viewWillAppear:(BOOL)animated{
camImage=Nil;
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"CamImage" inManagedObjectContext:self.managedObjectContext];
[request setReturnsObjectsAsFaults:NO];
[request setEntity:entity];
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[self.managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
}
// Set self's events array to the mutable array, then clean up.
[self setCamImage:mutableFetchResults];
viewWillAppear is not being called, because the parent view remains in the view hierarchy the whole time. Instead, implement navigationController:willShowViewController:animated: See this question: iOS 5 viewWillAppear not being called when popping a NavigationController
I am using the CoreDataBooks example code in my project and have implemented it nicely. I am attempting to add the ability to reorder the cells in the UITableView, however I am really struggling.
I have looked at a few techniques, the following seems the most logical and straightforward:
UITableView Core Data reordering
However, I can't get it working, the most suspicious thing being it includes a sort descriptor which might be conflicting with the sort descriptor implemented through the CoreDataBooks example, possible?
I can't pinpoint the problem.
Edit
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
// Create and configure a fetch request with the Book entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"GuestInfo" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
// Create the sort descriptors array.
NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:#"displayOrder" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] descriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Create and initialize the fetch results controller.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:#"firstName" cacheName:#"Root"];
self.fetchedResultsController = aFetchedResultsController;
fetchedResultsController.delegate = self;
return fetchedResultsController;
}
- (void)viewWillAppear {
myTableViewData = [self getRowObjects];
[self.tableView reloadData];
}
In my viewDidLoad this happens:
NSError *error;
if (![[self fetchedResultsController] performFetch:&error]) {
// Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
Does that call fetchedResultsController or throw an error if it doesn't exist? I can't see what else would cause the problem.
To pre-populate my Database for a small Iphone-App I do a check in the persistentStoreCoordinator Method in the AppDelegate if the sqlite-file is already there or not. If not I add some data into a table after the db is created. But the data should not directly shown in the RootViewController but in another TableView which can be accessed by pressing a Option in the RootViewController.
The Problem is that the data are saved but are not shown in the TableView. But if terminate and restart the app the data are there.
I have passed the managedObjectContext from my appDelegate to the the RootViewController and from there to the TableViewController. So the managedObjectContext is the same everywhere.
Here is the Code where I pre-populate the DB (in this example just one sample row):
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (persistentStoreCoordinator_ != nil) {
return persistentStoreCoordinator_;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:#"TestDBApp.sqlite"];
NSString *storePath = [storeURL relativePath];
BOOL noDb = false;
NSFileManager *fileManager = [NSFileManager defaultManager];
if( ![fileManager fileExistsAtPath:storePath]) {
noDb = true;
}
NSError *error = nil;
persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
if( noDb) {
noDb = false;
[self populateDB];
}
return persistentStoreCoordinator_;
}
- (void) populateDB {
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Kunde" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"oxid" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Root"];
NSError *error = nil;
if (![aFetchedResultsController performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
[self insertNewKunde:aFetchedResultsController];
[self saveContext];
[aFetchedResultsController release];
[sortDescriptors release];
[sortDescriptor release];
[fetchRequest release];
}
- (void)insertNewKunde:(NSFetchedResultsController *)fetchedResultsController {
// Create a new instance of the entity managed by the fetched results controller.
NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity];
NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];
// If appropriate, configure the new managed object.
[newManagedObject setValue:[[NSDate date] description] forKey:#"oxid"];
[newManagedObject setValue:#"Max" forKey:#"fname"];
[newManagedObject setValue:#"Mustermann" forKey:#"lname"];
// Save the context.
NSError *error = nil;
if (![context save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
The managedObjectContext is passed from the AppDelegate to the RootViewController as:
- (void)awakeFromNib {
RootViewController *rootViewController = (RootViewController *)[navigationController topViewController];
rootViewController.managedObjectContext = self.managedObjectContext;
}
and to the other TableViewController:
- (void)awakeFromNib {
kundenVC = [[KundenViewController alloc] initWithManagedObjectContext:self.managedObjectContext];
}
Can anyone help me or give a hint?
I also tried to reload the tableView through the viewWillAppear-Method. But no effect.
It is very difficult to guess what is happening but my hunch is that you are not calling self.populateDB until the RootViewController is actually created. This means the RootViewController does not see that data because it is not created.
I could be wrong but I guess that your last line in delegate's awakeFromNib method is eventually calling populateDB through self.managedObjectContext -> persistentStoreCoordinator -> self.populateDB.
Please try to add a line right at the top of awakeFromNib looking like this:
(void)awakeFromNib {
NSManagedObjectContext *context = self.managedObjectContext;
RootViewController *rootViewController = (RootViewController *)[navigationController topViewController];
rootViewController.managedObjectContext = context;}
This way I hope the your problem is solved because self.managedObjectContext will call the getter (- (NSManagedObjectContext)managedObjectContext;) instead of the field. Inside there (if you use the generated code) there is a call to the getter of ** persistentStoreCoordinator** which eventually calls you populateDB method.
In case that does not work go ahead and set a breakpoint inside your populateDB. When the debugger stops you should see at the method call stack where you populateDB is actually called from and that might help to figure out your problem.
-Andy
Well, the important part you left out to answer your question. What is [self saveContext] and how are you displaying the records in your table view.
Because your data is saved I assume that the code given here works. The only guess I can make is to use reset on the NSManagedObjectContext and then refetch.
BTW I like the "insertNewKunde" which seems to be the new German grammar ;-)
I'm a little stumped with an issue that I think goes back to my design.
I'm constructing a TableViewController based on a mainly static set of rows (4) - using that as a basis for a UITableView. Each row will kick off varying different views (detail, and UITableViews)... In my managed object context for the top view I can easily nav to the associated detail view because it's in context (nickname).. I initially thought about simply having unrelated tables and a series of buttons that would fire off the views... But I ditched that idea. My main current issue is knowing how to switch MOC or to different fetchedresults controllers (which are by the way defined in each .m to fetch from different tables.
At the moment, I've got a switch inside of TableViewControler.m.. This snipit works:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
NSInteger switchval = indexPath.row;
switch (switchval) {
case 0: // Nickname
{
//This version brings up a detailed view controller -
NickNameDetail *controller = [[NickNameDetail alloc] initWithNibName:#"NickNameDetail" bundle:nil];
controller.fetchedResultsController = self.fetchedResultsController;
controller.managedObjectContext = [self.fetchedResultsController objectAtIndexPath:indexPath];
[self.navigationController pushViewController:controller animated:YES];
break;
}
case 1:
{
//NextTableViewContoller *.... (etc)... here here
...
However, I can't figure out how to switch to a different context and get different rows.
meTableViewController.managedObjectContext = self.managedObjectContext;
nickNameDetail.managedObjectContext = self.managedObjectContext;
nextTableViewController.managedObjectContext = self.managedObjectContext;
Anyone run into a scenario like this before? Sorry, can't get the code formatter to behave.
Thanks!
In some cases it may be good/opportune to pass to the new view controller pushed on the navigation stack the MOC of your current view controller. However, you usually want to pass a newly created MOC. Do this as follows:
in your app delegate add the following method
- (NSManagedObjectContext*)createNewManagedObjectContext
{
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] init];
[moc setPersistentStoreCoordinator:[self persistentStoreCoordinator]];
return [moc autorelease];
}
in your view controller pass the MOC as follows
myAppDelegate *mainDelegate = (myAppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *mainMOC = [mainDelegate createNewManagedObjectContext];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(contextDidSave:)
name:NSManagedObjectContextDidSaveNotification
object:mainMOC];
newViewController.managedObjectContext = mainMOC;
and then handle the notification as needed, here is an example
- (void)contextDidSave:(NSNotification *)notification
{
[managedObjectContext mergeChangesFromContextDidSaveNotification:notification];
[self.tableView reloadData];
}
You also need to define and use a different NSFetchedResultsController for each of your view controllers. This is because the data you want to fetch and display are, of course, different for each view controller (different entity, predicate etc). Simply define them in each implementation file. Here is an example:
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
/*
Set up the fetched results controller.
*/
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Context" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
if(self.project){
// get the contexts for the project
NSPredicate * predicate = [NSPredicate predicateWithFormat: #"projectName == %#", self.project.name];
[request setPredicate:predicate];
}
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:YES selector:#selector(caseInsensitiveCompare:)];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request 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:request managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:nil];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[request release];
[sortDescriptor release];
[sortDescriptors release];
return fetchedResultsController;
}
and then use the fetchedResultsController as needed. For instance, put this in your viewDidLoad method:
NSError *error;
if (![[self fetchedResultsController] performFetch:&error]) {
// Handle error
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
I've got a basic photo album application, on the first view a list of albums is displayed with a subtitle showing how many images are in each album. I've got everything working to add albums, and add images to albums.
The problem is that the image count lines are accurate whenever the app loads, but I can't get them to update during execution.
The following viewdidload correctly populates all lines of the tableview when the app loads:
- (void)viewDidLoad {
[super viewDidLoad];
// Set the title.
self.title = #"Photo albums";
// Configure the add and edit buttons.
self.navigationItem.leftBarButtonItem = self.editButtonItem;
addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:#selector(addAlbum)];
addButton.enabled = YES;
self.navigationItem.rightBarButtonItem = addButton;
/*
Fetch existing albums.
Create a fetch request; find the Album entity and assign it to the request; add a sort descriptor; then execute the fetch.
*/
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Album" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
// Order the albums by name.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"albumName" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];
// Execute the fetch -- create a mutable copy of the result.
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
}
LocationsAppDelegate *mainDelegate = (LocationsAppDelegate *)[[UIApplication sharedApplication] delegate];
// Set master albums array to the mutable array, then clean up.
[mainDelegate setAlbumsArray:mutableFetchResults];
[mutableFetchResults release];
[request release];
}
But when I run similar code inside viewdidappear, nothing happens:
{
/*
Fetch existing albums.
Create a fetch request; find the Album entity and assign it to the request; add a sort descriptor; then execute the fetch.
*/
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Album" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];
// Order the albums by creation date, most recent first.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"albumName" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];
// Execute the fetch -- create a mutable copy of the result.
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
}
LocationsAppDelegate *mainDelegate = (LocationsAppDelegate *)[[UIApplication sharedApplication] delegate];
// Set master albums array to the mutable array, then clean up.
[mainDelegate setAlbumsArray:mutableFetchResults];
[self.tableView reloadData];
[mutableFetchResults release];
[request release];
}
Apologies if I've missed the answer to this question elsewhere, but what am I missing?
To troubleshoot, put NSLog statements in a few places in -viewDidAppear:. You would use these log statements to make sure that this method is both being called properly and to examine the contents of mutableFetchResults, at least.