这个例子使用了一个简单的两层层次结构的两个父亲Foo和Bar，每个有两个孩子，Foox，Foox和Barx，Barz分别，大纲视图是默认的只有两列和标识符第二列设置为children。

This example uses a simple two layer hierarchy of two parents Foo and Bar who each have two kids, Foox, Foox 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 = [NSDictionary dictionaryWithObjectsAndKeys:@"Foo",@"parent",[NSArray arrayWithObjects:@"Foox",@"Fooz", nil],@"children", nil];
NSDictionary *secondParent = [NSDictionary dictionaryWithObjectsAndKeys:@"Bar",@"parent",[NSArray arrayWithObjects:@"Barx",@"Barz", nil],@"children", nil];
NSArray *list = [NSArray arrayWithObjects:firstParent,secondParent, nil];


- (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;
}