Creating a Controller for NSOutlineView - objective-c

Question

I'm having an issue with regards to creating a separate Controller class for an NSOutlineView I have.
I've created a new class named LTSidebarViewController and in my MainMenu.xib file I've added an Object to the 'workbench' and linked it to my LTSidebarViewController class. I've also set the delegate and datasource to be linked to the NSOutlineView in MainMenu.xib.
What I am looking to do is create an instance of this class from within - (void)applicationDidFinishLaunching:(NSNotification *)aNotification in my AppDelegate file and when I do so I want to pass in the App Delegate's managedObjectContext. So, I've created a custom init method in LTSidebarViewController which looks like so:
-(id)initWithManagedObject:(NSManagedObjectContext*)managedObject{
self = [super init];
if (self) {
self.managedObjectContext = managedObject;
NSFetchRequest *subjectsFetchReq = [[NSFetchRequest alloc]init];
[subjectsFetchReq setEntity:[NSEntityDescription entityForName:#"Subject"
inManagedObjectContext:self.managedObjectContext]];
subjectsArray = [self.managedObjectContext executeFetchRequest:subjectsFetchReq error:nil];
_topLevelItems = [NSArray arrayWithObjects:#"SUBJECTS", nil];
// The data is stored in a dictionary
_childrenDictionary = [NSMutableDictionary new];
[_childrenDictionary setObject:subjectsArray forKey:#"SUBJECTS"];
// The basic recipe for a sidebar
[_sidebarOutlineView sizeLastColumnToFit];
[_sidebarOutlineView reloadData];
[_sidebarOutlineView setFloatsGroupRows:NO];
// Set the row size of the tableview
[_sidebarOutlineView setRowSizeStyle:NSTableViewRowSizeStyleLarge];
// Expand all the root items; disable the expansion animation that normally happens
[NSAnimationContext beginGrouping];
[[NSAnimationContext currentContext] setDuration:0];
[_sidebarOutlineView expandItem:nil expandChildren:YES];
[NSAnimationContext endGrouping];
// Automatically select first row
[_sidebarOutlineView selectRowIndexes:[NSIndexSet indexSetWithIndex:1] byExtendingSelection:NO];
}
return self;
}
I also have all the required methods in this class, - (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item etc.
Inside the - (void)applicationDidFinishLaunching:(NSNotification *)aNotification method in the App Delegate, I have the following:
LTSidebarViewController *sidebarViewController = [[LTSidebarViewController alloc] initWithManagedObject:self.managedObjectContext];
My problem is that this isn't working, I don't get any errors and the app runs but no data is displayed in the NSOutlineView.
Now from what I can tell the problem is that when the MainMenu.xib file is initially loaded, it's automatically creating an instance of my LTSidebarViewController class and calling it's init method but because my init method isn't doing anything the app doesn't finish launching correctly.
Am i taking the correct approach here? In simple terms all I'm looking for is to have a separate file that is used as the datasource for my NSOutlineView.

Answer 1

When working with NSOutlineView I generally put in extreme amounts of logging to figure out what's going on. I would probably do something like the following (maybe you have already done some of this):
Make sure you really have data in subjectsArray by logging it, e.g.
NSLog(#"subjectsArray");
NSLog(#"%#", subjectsArray);
Make sure you have implemented the NSOutlineView Datasource protocol methods from NSOutlineView Datasource Methods in your AppDelegate.m file and that they're returning the appropriate data.
If you need help implementing these, try a tutorial such as Source Lists and NSOutlineView.
I usually wind up with NSLog statements in each of the NSOutlineView data source methods to make sure they are being called and that I understand what each is expecting and returning.
Make sure your delegate and datasource are not nil for some reason in your initWithManagedObject:(NSManagedObjectContext *)managedObject method by logging them, e.g.
NSLog(#"datasource: %#", [self datasource]);
NSLog(#"delegate: %#", [self delegate]);
If you find that for some reason they are nil, you could manually set them just to make sure that's not the problem, e.g. in initWithManagedObject:
[self setDelegate: [NSApp delegate]];
[self setDatasource: [NSApp delegate]];
As far as whether this is the "correct" approach: I'm not clear from your code whether you're intending that the sideBarController is both the delegate and the datasource or whether the AppDelegate is serving those roles. Obviously, you'll need to implement the delegate and datasource protocols in the appropriate files. You certain can have AppDelegate serve those roles, although it seems to make more sense to have your sideBarController do that.
A small note: I sometimes access AppDelegate's managedObjectContext directly from supporting files with something like
-(NSManagedObjectContext *)managedObjectContext
{
return [[NSApp delegate] managedObjectContext];
}
rather than passing the managedObjectContext in manually to every file.