Text is not displayed in "SourceList" Outline View - objective-c

Question

I am using a "SourceList" OutlineView and cannot get the content of the "header" and "data" NSTableCellViews to display. The structure of the OutlineView works and my app runs and looks similar to this, http://i.stack.imgur.com/0E4D8.png.
Here is my code:
- (id)init {
self = [super init];
if (self) {
_masterFolder = [[NSMutableArray alloc] init];
MasterFolder *trueMaster = [[MasterFolder alloc] initMaster:#"Categories"];
[_masterFolder addObject:trueMaster];
[trueMaster addChild:[[MasterFolder alloc] initMaster:#"World"]];
[trueMaster addChild:[[MasterFolder alloc] initMaster:#"Sports"]];
[trueMaster addChild:[[MasterFolder alloc] initMaster:#"Local"]];
[trueMaster addChild:[[MasterFolder alloc] initMaster:#"Business"]];
[(MasterFolder *)[trueMaster.children objectAtIndex:0] addChild:[[MasterFolder alloc] initMaster:#"Middle East"]];
}
return self;
}
- (NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item {
return !item ? [self.masterFolder count] : [[item children] count];
}
- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item {
return !item ? YES : [[item children] count] != 0;
}
- (id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)index ofItem:(id)item {
return !item ? [self.masterFolder objectAtIndex:index] : [[item children] objectAtIndex:index];
}
- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item {
if (![item isKindOfClass:[MasterFolder class]]) {
return [outlineView makeViewWithIdentifier:#"HeaderCell" owner:self];
} else {
NSTableCellView *cellView = [outlineView makeViewWithIdentifier:#"DataCell" owner:self];
cellView.textField.stringValue = [((MasterFolder *)item) name];
return cellView;
}
}
I know it is an issue with this function:
- (NSView *)outlineView:(NSOutlineView *)outlineView viewForTableColumn:(NSTableColumn *)tableColumn item:(id)item {
but I do not know what to change to make it work. I have viewed a lot of similar posts on Stack Overflow already, and was not able to get the solutions that were offered to work.