I'm having an issue with Core Data. I have an Array Controller setup that links the data to an NSTableView.
I have a function that runs code every few seconds and in it I display the list of files
NSEntityDescription *entity = [NSEntityDescription entityForName:#"File"
inManagedObjectContext:[self managedObjectContext]];
[request setEntity:entity];
NSError *error = nil;
NSArray *fetchedObjects =[_managedObjectContext executeFetchRequest:request
error:&error];
for (NSManagedObject *objectt in fetchedObjects) {
NSLog(#"Object Name: %#", [objectt valueForKey:#"filename"]);
}
NSManagedObject *object = [fetchedObjects objectAtIndex:index];
NSLog(#"Filename: %#, Index: %ld", [object valueForKey:#"filename"], index);
NSString *imageName = [object valueForKey:#"imageName"];
NSImage *image = [object valueForKey:#"taggedImage"];
First time this code is ran the list matches the table columns. When it's ran again what's fetched from the array controller has changed, but not the tableview. So it's not in sync anymore.
The values at the same index for the table and array are different.
Have you manually checked your NSArrayController to see if it is in sync? That would narrow the question down to is the NSArrayController misconfigured or is the NSTableView misconfigured. Your statement claims you are looking at the NSArrayController but when you use the word fetched I worry you are confusing the objects.
Also, is the data in a saved state or still in an unsaved state? That question also impacts display from the NSArrayController and NSTableView.
Related
I am using NSArrayController Binding to populate NSTableView from core data. NSArrayController is connected to mainQueueConcurrencyType managed object context(main managed object).
parent of main managed object context is privateQueueConcurrencyType (background managed object context). Save call on main managed object context will push changes to background managed object context and save on background managed object context will save to persistent store.
Prepares contents and Editable are enabled in xib for NSArrayController
Core data table :
Path
Date
Status
I have unique constraints added to path.
Sometimes NSArrayController is not removing deleted object from arranged object after core data save.
[context performBlock:^{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"entity" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"path ==%#", path];
[fetchRequest setPredicate:predicate];
NSError *error = nil;
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
SyncStatusEntry *syncStatus = [fetchedObjects firstObject];
NSInteger status = syncStatus.status.integerValue;
context deleteObject:syncStatus];
[context save:nil];
// Sometimes NSArrayController still have this object
}];
Can anyone please help me out?
Apparently NSArrayController is notified when something changes in the context. This notification is sent in mergeChangesFromContextDidSaveNotification: which is automatically called if automaticallyMergesChangesFromParent is YES.
I have 3 entities in my data model which are connected as follow:
User<-->>Performance<-->>Trials
Meaning that every user has several performances, in each he/she goes under several trials.
For each entity, I have one table view and one array controller object. For all, I have bound their Managed Object Context parameter to App Delegate.
Then I bound PerformanceArrayController to UserArrayController Content Set (Controller Key: selection and performances relationship). And the same for TrialArrayController: I bound it to PerformanceArrayController (on selection) and trials relationship.
I have no problem in binding single columns of User table view and performance table view to entities attributes. but when I want to do the same for trial table view, first I don't get autocompletion and second when I write the name of the attributes manually, I get a gray exclamation mark. and only the first trial is saved this way but not the rest of them.
Here is my function for inserting into Trial:
- (void) insertIntoTrial: (NSString *) result
{
NSManagedObjectContext *context = [self managedObjectContext];
NSError *error;
Trial *trial = [NSEntityDescription insertNewObjectForEntityForName:#"Trial" inManagedObjectContext:context];
trial.result = result;
trial.time = [NSNumber numberWithDouble:[cueTimestamp timeElapsedInSeconds]];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Performance" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"user.fName==%#", userName]];
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
for (Performance *performance in fetchedObjects) {
[performance addTrialsObject:trial];
trial.performance = performance;
}
if (![context save:&error]) {
NSLog(#"couldn't save Trial info: %#", [error localizedDescription]);
}
}
Thanks in advance,
I am a VERY new beginner to Core Data and I have recently been trying to read and write data. I created an entity named "Person" with the entities "name" and "age". I also have a textfield name "personName" and a textfield named "personAge".
- (IBAction)readData:(id)sender
{
NSNumber *ageNum = [NSNumber numberWithInteger:personAge.text.integerValue];
Person *newPerson = [NSEntityDescription insertNewObjectForEntityForName:#"Person" inManagedObjectContext:managedObjectContext];
newPerson.name = personName.text;
newPerson.age = ageNum;
NSLog(#"Person %# name is %#", personName.text, ageNum);
}
When I load the app, all i get is SIGABRT. Even when all I put in the method is
Person *newPerson = [NSEntityDescription insertNewObjectForEntityForName:#"Person" inManagedObjectContext:managedObjectContext];
All help is appreciated.
For Adding values to the core data you can do so:-
- (IBAction)save:(id)sender {
NSManagedObjectContext *context = [self managedObjectContext];
// Create a new managed object
NSManagedObject *person = [NSEntityDescription insertNewObjectForEntityForName:#"Person" inManagedObjectContext:context];
[person setValue:self.personName.text forKey:#"name"];
[person setValue:self.personAge.text forKey:#"age"];
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}
}
For fetching the values from core data:-
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Person"];
self.personValues = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];
here personValues is a NSMutableArray.
For better understanding about these please go through this link.
http://www.appcoda.com/introduction-to-core-data/
Hope this will help you out.
If you are very new to Core Data, try using the MagicalRecord library which provides a series of helper categories for dealing with a lot of the boiler plate setup of Core Data.
Which brings me to the question you are asking: are you sure your Core Data stack is being setup correctly? Check to make sure your Managed Object Context is valid along with a proper Persistent Store Coordinator.
Best thing to do: put a breakpoint during the Core Data stack setup and step through it making sure everything is setup properly. Or install MagicalRecord and do one method call to [MagicalRecord setupAutomigratingCoreDataStack]...
I'm working on an iPhone app that gets a number of objects from a database. I'd like to store these using Core Data, but I'm having problems with my relationships.
A Detail contains any number of POIs (points of interest). When I fetch a set of POI's from the server, they contain a detail ID. In order to associate the POI with the Detail (by ID), my process is as follows:
Query the ManagedObjectContext for the detailID.
If that detail exists, add the poi to it.
If it doesn't, create the detail (it has other properties that will be populated lazily).
The problem with this is performance. Performing constant queries to Core Data is slow, to the point where adding a list of 150 POI's takes a minute thanks to the multiple relationships involved.
In my old model, before Core Data (various NSDictionary cache objects) this process was super fast (look up a key in a dictionary, then create it if it doesn't exist)
I have more relationships than just this one, but pretty much every one has to do this check (some are many to many, and they have a real problem).
Does anyone have any suggestions for how I can help this? I could perform fewer queries (by searching for a number of different ID's), but I'm not sure how much this will help.
Some code:
POI *poi = [NSEntityDescription
insertNewObjectForEntityForName:#"POI"
inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]];
poi.POIid = [attributeDict objectForKey:kAttributeID];
poi.detailId = [attributeDict objectForKey:kAttributeDetailID];
Detail *detail = [self findDetailForID:poi.POIid];
if(detail == nil)
{
detail = [NSEntityDescription
insertNewObjectForEntityForName:#"Detail"
inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]];
detail.title = poi.POIid;
detail.subtitle = #"";
detail.detailType = [attributeDict objectForKey:kAttributeType];
}
-(Detail*)findDetailForID:(NSString*)detailID {
NSManagedObjectContext *moc = [[UIApplication sharedApplication].delegate managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription
entityForName:#"Detail" inManagedObjectContext:moc];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entityDescription];
NSPredicate *predicate = [NSPredicate predicateWithFormat:
#"detailid == %#", detailID];
[request setPredicate:predicate];
NSLog(#"%#", [predicate description]);
NSError *error;
NSArray *array = [moc executeFetchRequest:request error:&error];
if (array == nil || [array count] != 1)
{
// Deal with error...
return nil;
}
return [array objectAtIndex:0];
}
Check out the section titled "Batch Faulting" on the page titled "Core Data Performance" in Xcode's Core Data Programming Guide that Norman linked to in his answer.
Only fetching those managedObjects whose ids are IN a collection (NSSet, NSArray, NSDictionary) of ids of the objects returned by the server may be even more efficient.
NSSet *oids = [[NSSet alloc] initWithObjects:#"oid1", #"oid2", ..., nil];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"oid IN %#", oids];
[oids release];
UPDATE: I worked this tip into a solution for the acani usersView. Basically, after downloading a JSON response of users, the iPhone uses the popular open source JSON framework to parse the response into an NSArray of NSDictionary objects, each representing a user. Then, it makes an NSArray of their uids and does a batch fetch on Core Data to see if any of them already exist on the iPhone. If not, it inserts it. If so, it updates the ones that do exist only if their updated attribute is older than that of the one from the server.
I've gotten all this to work really well, thanks to Norman, who put me on the right path. I'll post my helper class here for others.
Basically, my helper class will look up if an NSManagedObject exists for some ID, and can create it for some ID. This executes quickly enough for me, with 1,000 find/create operations taking around 2 seconds on my iPhone (I also did a few other things there, pure find/create is likely faster).
It does this by caching a dictionary of all the NSManagedObjects, and checking that cache rather than executing a new NSFetchRequest.
A couple of modifications that could help things speed up even further:
1. Get only selected properties for the NSManagedObjects
2. Only get the identifier property for the NSManagedObject into a dictionary, instead of the whole object.
In my performance testing, the single query wasn't the slow part (but with only 1,000 items, I'd expect it to be fast). The slow part was the creation of the items.
#import "CoreDataUniquer.h"
#implementation CoreDataUniquer
//the identifying property is the field on the NSManagedObject that will be used to look up our custom identifier
-(id)initWithEntityName:(NSString*)newEntityName andIdentifyingProperty:(NSString*)newIdProp
{
self = [super init];
if (self != nil) {
entityName = [newEntityName retain];
identifyingProperty = [newIdProp retain];
}
return self;
}
-(NSManagedObject*)findObjectForID:(NSString*)identifier
{
if(identifier == nil)
{
return nil;
}
if(!objectList)
{
NSManagedObjectContext *moc = [(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription
entityForName:entityName inManagedObjectContext:moc];
NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:entityDescription];
NSError *error;
NSArray *array = [moc executeFetchRequest:request error:&error];
objectList = [[NSMutableDictionary dictionary] retain];
for (NSManagedObject* p in array) {
NSString* itemId = [p valueForKey:identifyingProperty];
[objectList setObject:p forKey:itemId];
}
}
NSManagedObject* returnedObject = [objectList objectForKey:identifier];
return returnedObject;
}
-(NSManagedObject*)createObjectForID:(NSString*)identifier
{
NSManagedObject* returnedObject = [NSEntityDescription
insertNewObjectForEntityForName:entityName
inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]];
[returnedObject setValue:identifier forKey:identifyingProperty];
[objectList setObject:returnedObject forKey:identifier];
return returnedObject;
}
- (void) dealloc
{
DESTROY(entityName);
DESTROY(identifyingProperty);
[super dealloc];
}
#end
This page provides some help on optimizing performance:
http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/Articles/cdPerformance.html#//apple_ref/doc/uid/TP40003468-SW1
While not very efficient, why not just build them in-memory with a NSDictionary? Read everything from Core Data into a NSDictionary then merge in your data, replacing everything in Core Data.
I have an optional binary attribute: image, containing an image for my entities.
In the interface, I have NSImageView (Image Well), and a "Remove Image" button. When the image removing button is clicked, I do:
- (IBAction)saveAction:(id)sender {
NSError *error = nil;
if (![[self managedObjectContext] save:&error]) {
[[NSApplication sharedApplication] presentError:error];
}
[tableView reloadData];
}
- (IBAction)removeImage:(id)sender {
[image setImage:nil]; // image is a NSImageView outlet bound to the image attribute.
[self saveAction:sender];
}
It clears the image from the NSImageView, but the binary data is still retained in the Core Data entity.
How do I reflect the change in the Core Data entity as well?
Thanks!
Edit:
NSImageView is already bound to model's image attribute, and available as outlet too. So I'm just looking for someone to tell me how to reset the attribute by fetching the model (if that's what I need to do).
Would appreciate any code help. :)
[image setImage:nil];
Is image actually an image view? If so, I must remind you to name your instance variables clearly and accurately.
You need to set the image property of the model object(s), not the view(s). Bind the views through the controllers to the model; then, when you change the model, the views pick up the changes for free.
I was under impression that altering an array from a fetch request won't make a difference to the actual data in storage. But I was wrong. I tried and it worked! Thanks Peter, and everyone elsewhere!
Here's what I replaced my image removal function for currently selected entity having a unique attribute:
- (IBAction)removeImage:(id)sender {
// Fetch the entity in question.
NSManagedObjectContext *context = [self managedObjectContext];
NSManagedObjectModel *model = [self managedObjectModel];
NSEntityDescription *entity = [[model entitiesByName] valueForKey:#"myEntity"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:
#"unique_attr == %#", [unique_attr_outlet stringValue]];
NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
[fetch setEntity:entity];
[fetch setPredicate:predicate];
// Load it into NSArray object and remove the binary data attribute.
NSArray *contextArray = [context executeFetchRequest:fetch error:nil];
if ([contextArray count] > 0)
[[contextArray objectAtIndex:0] setValue:nil forKey:#"myImage"];
[fetch release];
}