How to Save Entity with Relationship in Core Data - ios

Question

I'm new to Core Data, so go easy on me. :) I'm currently using iOS 7 in Xcode 5.
I have two Entities: Aircraft and Entry. There is a one aircraft to many entry relationship.
I'm trying to save a new Entry which has an aircraft object in it. Here is my Entry.h file (minus the #import):
// Entry.h
#class Aircraft;
#interface Entry : NSManagedObject
#property (nonatomic, retain) NSNumber *duration;
#property (nonatomic, retain) NSDate *flightDate;
#property (nonatomic, retain) Aircraft *aircraft;
#end
Meanwhile, over in my view controller where I save the new Entry, I have the following code. I use a dictionary to set up my data prior to creating a new record:
//Add New Entry
Aircraft *aircraft = [Aircraft new];
aircraft.aircraftRegistration = _aircraftRegistrationTextField.text;
NSDictionary *newEntry = #{
#"aircraft": aircraft, //???
#"flightDate": [formatter dateFromString:_flightDateTextField.text],
#"duration": [PPHelpers convertHHMMtoDecimal:_durationTextField.text],
};
//Save new Entry to Core Data
PPAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSManagedObject *item = [NSEntityDescription insertNewObjectForEntityForName:#"Entry" inManagedObjectContext:context];
[item setValuesForKeysWithDictionary:newEntry];
NSError *error;
[context save:&error];
I get a couple errors from this:
CoreData: error: Failed to call designated initializer on NSManagedObject class 'Aircraft'
and...
-[Aircraft setAircraftRegistration:]: unrecognized selector sent to instance 0x110b0b550
I suspect the issue is that I'm not adding the Aircraft to the Entry in the right way.
Any ideas what I'm doing wrong?

Answer 1

Aircraft *aircraft = [Aircraft new];
creates an object without calling the designated initializer. You should replace it by
Aircraft *aircraft = [NSEntityDescription insertNewObjectForEntityForName:#"Aircraft" inManagedObjectContext:context];
Note: It is possible to set Core Data attributes with setValuesForKeysWithDictionary,
but a more direct, type-safe and less error-prone way would be to use the Core Data
accessors:
Entry *entry = [NSEntityDescription insertNewObjectForEntityForName:#"Entry" inManagedObjectContext:context];
entry.aircraft = aircraft; // from above
entry.duration = ...;
entry.flightData = ...;

Answer 2

if Aircraft is an parent relation entity, you need to use instanciate it by insertNewObjectForEntityForName it's the same that Entry.
//Save new Entry to Core Data
PPAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
//Add New aircraft
Aircraft* aircraft = (Aircraft*) [NSEntityDescription insertNewObjectForEntityForName:[NSClassFromString(Aircraf) inManagedObjectContext:context];
aircraft.aircraftRegistration = _aircraftRegistrationTextField.text;
Entry* item = (Entry*) [NSEntityDescription insertNewObjectForEntityForName:NSClassFromString(Entry) inManagedObjectContext:context];
[item setAircraft:aircraft];
[item setFlightDate:[formatter dateFromString:_flightDateTextField.text]];
[item setDuration:[PPHelpers convertHHMMtoDecimal:_durationTextField.text]];
NSError *error;
[context save:&error];