Question

I’ve got an NSMutableArray that currently holds a bunch of Core Data entities like so:

NSFetchRequest *fetchReq = [[NSFetchRequest alloc]init];
[fetchReq setEntity:[NSEntityDescription entityForName:@"Subject"
                                inManagedObjectContext:self.managedObjectContext]];

subjectsArray = [self.managedObjectContext executeFetchRequest:fetchReq error:nil];

I then put this array in a dictionary:

_childrenDictionary = [NSMutableDictionary new];
[_childrenDictionary setObject:subjectsArray forKey:@"SUBJECTS"];

This dictionary is then used as the data for a Source List I have implemented. What I’m having issues with is deleting an object from the subjectsArray. I’ve tried this with the following code:

_selectedSubject = [subjectsArray objectAtIndex:0];
[subjectsArray removeObject:subjectToDelete];

Now this works fine, when I execute the following:

for (Subject *s in subjectsArray) {
        NSLog(@"Subjects: %@", [s title]);
    }

The Subject I selected to delete is no longer there and the Source List I have updates correctly after calling:

[_sidebarOutlineView reloadData];

The problem I am having though is that when I quit the application and open it up again, the Subject I previously deleted is still there.

The fetching of the core data entities into the array and dictionary is done inside applicationDidFinishLaunching. At the moment all this code is inside the AppDelegate file, which has a .h file that looks like this:

#import <Cocoa/Cocoa.h>
#import "Subject.h"

@interface LTAppDelegate : NSObject <NSApplicationDelegate, NSOutlineViewDelegate,     NSOutlineViewDataSource, NSMenuDelegate> {
    IBOutlet NSWindow *newSubjectSheet;
    IBOutlet NSWindow *newNoteSheet;
    IBOutlet NSWindow *newEditSheet;
    NSMutableArray *subjectsArray;
}

@property Subject *selectedSubject;
@property (assign)IBOutlet NSOutlineView *sidebarOutlineView;
@property NSArray *topLevelItems;
@property NSViewController *currentContentViewController;
@property NSMutableDictionary *childrenDictionary;
@property NSArray *allSubjects;

Any ideas as to what is causing to deleted Subject to reappear?

Answer 1

You are removing the objects from the local array, but not the CoreData store itself.

To remove an object from the Core Data store, you need to call managedObjectContext
deleteObject:theObject on it, and then call managedObjectContent save:&error to persist it.

If you are using table views, I would recommend checking out the NSFetchedResultsController as well.