Dear list,
I have a simple core-data model with an entity 'Category' and an
entity 'Note'. The 'Category' entity has a to-many relationship
'notes' to entity type 'Note'.
The categories are displayed in an outline view via a tree controller.
There is also a table which displays the contents of an array
controller (NotesArrayController) - this is supposed to show a subset
of the notes.
I have a switch on the UI which is meant to let the user choose
whether to display all notes in the currently selected category, or
all notes from all categories. So I want to modify the content of
NotesArrayController depending on the state of the switch.
So far I tried doing this programatically with bindings using the two
methods below (actually the switching mechanism is just two buttons).
This works as far as displaying the correct content to the user, but
when it comes to deleting objects when in 'all categories' mode, it
doesn't work properly. I get messages in the console like:
*** -[NSCFArray removeObjectAtIndex:]: mutating method sent to
immutable object
So that's pretty clear, and I'm obviously going about this in the
wrong way. The question is, what is a proper way to handle this?
Thanks in advance for any constructive comments,
Martin
#pragma mark -
#pragma mark Category control
- (IBAction)allCategoriesSelected:(id)sender
{
[singleCategoryButton setState:0];
[allCategoriesButton setState:1];
[notesArrayController unbind:@"contentSet"];
[notesArrayController unbind:@"contentArrayForMultipleSelection"];
[notesArrayController setContent:nil];
NSManagedObjectContext *moc = managedObjectContext;
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:@"Note"
inManagedObjectContext:moc]];
NSError *error = nil;
NSArray *results = [moc executeFetchRequest:request error:&error];
if (error) {
[NSApp presentError:error];
[request release];
return;
}
[notesArrayController setContent:results];
[request release];
}
- (IBAction)singleCategorySelected:(id)sender
{
[allCategoriesButton setState:0];
[singleCategoryButton setState:1];
[notesArrayController unbind:@"contentSet"];
[notesArrayController unbind:@"contentArrayForMultipleSelection"];
[notesArrayController setContent:nil];
NSDictionary *dict = [NSDictionary dictionaryWithObject:[NSNumber
numberWithBool:YES]
forKey:NSDeletesObjectsOnRemoveBindingsOption];
// bind contents to entries in the selected categories
[notesArrayController bind:@"contentSet"
toObject:treeController
withKeyPath:@"selection.notes" options:dict];
// so that multiple selected categories works properly but this is
not really
// necessary since we don't allow multiple selection on the outline
view at the
// moment.
[notesArrayController bind:@"contentArrayForMultipleSelection"
toObject:treeController
withKeyPath:@"selecti...@distinctunionofarrays.notes"
options:nil];
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Martin Hewitson
Albert-Einstein-Institut
Max-Planck-Institut fuer
Gravitationsphysik und Universitaet Hannover
Callinstr. 38, 30167 Hannover, Germany
Tel: +49-511-762-17121, Fax: +49-511-762-5861
E-Mail: martin.hewit...@aei.mpg.de
WWW: http://www.aei.mpg.de/~hewitson
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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