Problem adding an entity to a to-many relationship
Problem adding an entity to a to-many relationship
- Subject: Problem adding an entity to a to-many relationship
- From: Keith Lander <email@hidden>
- Date: Tue, 30 Dec 2008 15:00:30 +0000
I am trying to get my head round Core Data and Bindings. I have
created a simple core data model consisting of two entities called
Course and Student. There is a to-many relationship from Course to
Student. I have created a view with one table for Courses and another
for students. There is a button for adding courses. That works fine. I
also have a button which when clicked gets a CSV file containing
student details. For each student in the file I want to create a new
entity and have the following code in my NSPersistentDocument subclass:
NSManagedObjectContext *context = [self managedObjectContext];
Student *student = [NSEntityDescription
insertNewObjectForEntityForName:@"Student"
inManagedObjectContext:context];
This seems to work OK. I then update the fields with data from the CSV
file.
The problem comes when I try to add the student to its owning course.
I get the course from the array controller using:
Course *course = [[coursesController selectedObjects] objectAtIndex:0];
This seems to return the correct entity.
Then I then add the student using the predefined accessor:
[course addStudentsObject:student];
This fails in the call [NSBinder
_invokeSelector:withAguments:onKeyPath:ofObject:mode:raisesForNotApplicableKeys
:]
I'm using the latest version of XCode and have got garbage collection
switched on.
I hope someone can sort me out.
Cheers
Keith
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