[Nitro] Og and the 'Composite' pattern.

[Alexey Petrushin]

Hello, is there a way to implement the 'Composite' pattern in Og?

Probably it should looks like this:

class Item
property :name, String
belongs_to :parent, Item
end

class Container < Item
has_many :items, Item
end

class Image < Item; end
class Post < Item; end
class Folder < Container; end

But i failed to achieve this with Og :(

P.S.
Does ActiveRecords or DataMapper support this feature?

Thanks!
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[Alexey Petrushin]

Partially solution. It's possible to implement subject this way:

class Item
property :name, String

belongs_to :parent, Object
end

class Container < Item
has_many :items, Item
end

class Folder < Item
has_many :items, Item
end

But, there are major disadvantages:
- Code duplication, each 'Container' should explicitly include 'has_many
...'.
- Instead of 'Item' you forced to use 'Container::Item' and
'Folder::Item' and remember about it.
- Instead of one 'Item' table you got two distinct 'container_item' and
'folder_item' tables.

So, this is not the best solution ... :(

[* William]

Thanks there Alexey

I love this post!  I have a design need for exactly thing like (both) 'Item' and 'Container'. 

As well, I'd like to make a "generic" 'Container' that cna accept 'Items" sub-clases too.

I'd like though to do ...

            class Data_Table_stuff
                property     subclass-of-Item
                property     subclass-of-Container

            end # Data_Table_stuff

I'll admit that I'm sitting back on this.  My issuer -- Still some solid Og base is a precursor.

:-)

2008/6/6 Alexey Petrushin <li...@ruby-forum.com>:

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aloha,
\_w_/