Question

Please, could you give a simple complete example of Cocoa application with NSOutlineView with hierarchical data representation not so ambiguous like NSOutlineView and NSTreeController example
.

Thanks!

Answer 1

This example uses a simple two layer hierarchy of two parents Foo and Bar who each have two kids, Foox, Fooz and Barx, Barz respectively, the outline view is the default one with just two columns and the identifier of the second column is set to “children”.

NSDictionary *firstParent = @{@"parent": @"Foo", @"children": @[@"Foox", @"Fooz"]};
NSDictionary *secondParent = @{@"parent": @"Bar", @"children": @[@"Barx", @"Barz"]};
NSArray *list = @[firstParent, secondParent];

- (BOOL)outlineView:(NSOutlineView *)outlineView isItemExpandable:(id)item
{        
    if ([item isKindOfClass:[NSDictionary class]]) {
        return YES;        
    }else {
        return NO;
    }
}

- (NSInteger)outlineView:(NSOutlineView *)outlineView numberOfChildrenOfItem:(id)item
{    

    if (item == nil) { //item is nil when the outline view wants to inquire for root level items
        return [list count];                 
    }   

    if ([item isKindOfClass:[NSDictionary class]]) {
        return [[item objectForKey:@"children"] count];
    }

    return 0;
}

- (id)outlineView:(NSOutlineView *)outlineView child:(NSInteger)index ofItem:(id)item
{

    if (item == nil) { //item is nil when the outline view wants to inquire for root level items
        return [list objectAtIndex:index];                   
    }

    if ([item isKindOfClass:[NSDictionary class]]) {
        return [[item objectForKey:@"children"] objectAtIndex:index];
    }     

    return nil;
}

- (id)outlineView:(NSOutlineView *)outlineView objectValueForTableColumn:(NSTableColumn *)theColumn byItem:(id)item
{          

    if ([[theColumn identifier] isEqualToString:@"children"]) {
        if ([item isKindOfClass:[NSDictionary class]]) {
            return [NSString stringWithFormat:@"%i kids",[[item objectForKey:@"children"] count]];
        }  
        return item;
    }else{
        if ([item isKindOfClass:[NSDictionary class]]) {
            return [item objectForKey:@"parent"];                         
        }           
    }

    return nil;
}