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,
Related
I have a core data entity, "Entity 1" it has a one to many relationship lets call it "entityRelationship" to another entity "Entity 2".
I'd like to be able to perform a NSFetchRequest for use with a NSFetchResultsController to return the list of "Entity 2" objects for a specific "Entity 1" object.
I have the "Entity 1" stored out as it's own variable, but i can't seem to find the correct way to set up an NSPredicate to return the objects:
Here's my code:
NSFetchedResultsController *fetchedEvents;
NSFetchRequest *fetchRequest;
NSError *error = nil;
fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Entity2"];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"Entity2 IN self = %#",entity1Object]];
[fetchRequest setSortDescriptors:#[]];// no sort descriptors
fetchedEvents = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:theManagedObjectContext sectionNameKeyPath:nil cacheName:nil];
[fetchedEvents performFetch:&error];
if (error) {
NSLog(#"Unable to perform fetch.");
NSLog(#"%#, %#", error, error.localizedDescription);
}
return fetchedEvents;
This crashes with the following error:
** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "NSMDEvents IN self = %#"'
Am i doing something wrong? Or is this the incorrect way to go about returning entities with relationships?
Since you have entity1Object and the defined relationship, you can retrieve the Entity2 objects directly from there
NSSet *entity2Objects = [entity1Object valueForKey:#"entityRelationship"];
An extra fetch is not needed.
But if you really need the fetch define a reverse relationship and use a property with an unique value.
For example let's assume that entity1 are clubs and entity2 are their members and you want to get all members for a specific club use this predicate:
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Member"];
[NSPredicate predicateWithFormat:#"club.name == %#", currentClub.name];
The literal club in the predicate is the reverse relationship object.
Or translated to your example
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Entity2"];
[NSPredicate predicateWithFormat:#"entity1.property == %#", entity1Object.property];
Trying the suggested code (thanks vadian) kept causing my app to crash with various errors regarding keys not existing etc, this turned out to be down to a relationship issue.
"Entity2" was inheriting from another entity (had its parent Entity field set in the Data Model Inspector)"Entity 0". However the relationship between "Entity1" was between itself and "Entity0" not "Entity2".
So after a rejig of the core data model "Entity2" had a relationship added (lets call it "EntityEvents") between itself and "Entity1". Now using the following code i was able to select the specific events from the current object:
NSFetchedResultsController *fetchedEvents;
NSFetchRequest *fetchRequest;
NSError *error = nil;
fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Entity2"];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"EntityEvents == %#",Entity1]];
[fetchRequest setSortDescriptors:#[]];// no sort descriptors
fetchedEvents = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:theManagedObjectContext sectionNameKeyPath:nil cacheName:nil];
[fetchedEvents performFetch:&error];
if (error) {
NSLog(#"Unable to perform fetch.");
NSLog(#"%#, %#", error, error.localizedDescription);
}
return fetchedEvents;
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 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.
I have the following Core Data model (simplified for example):
Person
->Address
City
>Region
RegionName
>Country
CountryName
When a new Person is created
NSManagedObjectModel *objectModel=[[AppCoreData sharedInstance]objectModel];
NSEntityDescription *entity=[[objectModel entitiesByName] valueForKey:#"Beverage"];
Person *person=(Person*)[[NSManagedObject alloc]initWithEntity:entity insertIntoManagedObjectContext:nil];
a Person entity is created w/o inserting into the object context so it is easy to abandon the insert if necessary.
Then the user can select a Region which may or may not exist in the database. A search is performed to see if the Region exists
NSEntityDescription *entityDescription=[NSEntityDescription entityForName:#"Region" inManagedObjectContext:self.objectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDescription];
request.returnsObjectsAsFaults=NO;
NSPredicate *predicate=[NSPredicate predicateWithFormat:#"id == %#",region.id];
[request setPredicate:predicate];
NSError *error=nil;
NSArray *array= [self.objectContext executeFetchRequest:request error:&error];
if ([array count] == 1) {
//use existing object
person.region=(Region*)[array objectAtIndex:0];
} else {
//create new object
NSEntityDescription *entity=[[objectModel entitiesByName] valueForKey:#"Region"];
self.collectionItem.beverage.region=(Region*)[[NSManagedObject alloc]initWithEntity:entity insertIntoManagedObjectContext:nil];
person.region.id=[NSNumber numberWithInt:[regionID intValue]];
person.region.regionName=regionName;
}
Finally, if the user does not abandon the insert, the person object is inserted into the object context and saved
[self.objectContext insertObject:self.collectionItem];
What is the best approach to dealing with nested Core Data objects where the nested objects, e.g., Region may or may not exist in Core Data? Examples or references appreciated.
Standard newbie question. I've created a data model for an iOS application. I am able to create, update and delete entities within the model from various views by using the NSEntityDescription object.
Say if I had a mutable array of objects returned from a fetch request. How can I loop through each one when I do not have a generated object definition from the entity model? By generated object definition I mean, a header and body class definition of the entity described in the data model package.
All CoreData entities derive from NSManagedObject and all the database data from those can be accessed via key value encoding. The minimum you need to know can be gained from the Model. You don't necessarily require the headers.
For example an entity PersonEntity which has a relationship to NameEntity with attribute firstname
NSArray *results = [managedObjectContext queryEntityForName:#"PersonEntity" predicateFormat:nil argumentArray:nil];
for(NSManagedObject *object in results)
{
NSString *name = [object valueForKeyPath:#"nameobject.firstname";
[self doSomething:name];
}
queryEntityForName is my own category. You might find it useful.
#implementation NSManagedObjectContext(VMQueryAdditions)
-(NSArray *)queryEntityForName:(NSString *)name predicateFormat:(NSString *)pstring argumentArray:(NSArray *)arr
{
NSEntityDescription *entity = [NSEntityDescription entityForName:name inManagedObjectContext:self];
NSFetchRequest *fetch = [[[NSFetchRequest alloc] init] autorelease];
[fetch setEntity:entity];
NSPredicate *pred;
if(pstring)
{
if(arr) pred = [NSPredicate predicateWithFormat:pstring argumentArray:arr];
else pred = [NSPredicate predicateWithFormat:pstring];
[fetch setPredicate:pred];
}
NSError *error = nil;
NSArray *results = [self executeFetchRequest:fetch error:&error];
if (error) {
NSLog(#"MOC Fetch - Unresolved error %#, %#", error, [error userInfo]);
return [NSArray array];
}
return results;
}
#end