Self referential model?

is it possible to have a model be belong to itself?

say i have a category, and the category can be a subcategory of another
category (or it might be a parent category)…

is this possible, and does it make sense?

something like:

class Category < ActiveRecord::Base
has_many: categories
end

i kinda think it would make more sense to use a subcategory model… but
the system i am deriving from (which was written in php) is combining
the models…

thanks!

Robert W. wrote:

Sergio R. wrote:

is it possible to have a model be belong to itself?

There is also the http://github.com/rails/acts_as_tree/ plugin that
implements a simple tree structure and may be adequate for your needs.

Sergio R. wrote:

is it possible to have a model be belong to itself?

say i have a category, and the category can be a subcategory of another
category (or it might be a parent category)…

http://github.com/collectiveidea/awesome_nested_set/

is this possible, and does it make sense?

Yes, it makes sense.

something like:

class Category < ActiveRecord::Base
has_many: categories
end

i kinda think it would make more sense to use a subcategory model… but
the system i am deriving from (which was written in php) is combining
the models…

No. As you’ll see from the above plugin using one model does make more
sense.

thanks, guys… installed awesome_nested_set now… playing with it…
looks cool…

i am guessing that there is no drop in method of using this with
active_scaffold… correct?

anyway…

this looks great!

thanks!

you can read rails guides.
http://guides.rubyonrails.org/association_basics.html#polymorphic-associations

class Employee < ActiveRecord::Base
has_many :subordinates, :class_name => “Employee”, :foreign_key =>
“manager_id”
belongs_to :manager, :class_name => “Employee”
end

With this setup, you can retrieve @employee.subordinates and
@employee.manager.

2009/10/27 Sergio R. [email protected]:

class Category < ActiveRecord::Base


tommy xiao
E-mail: xiaodsATgmail.com

Sergio R. wrote:

thanks, guys… installed awesome_nested_set now… playing with it…
looks cool…

awesome_nested_set is great. If you’re not already familiar with nested
sets, make sure to read Joe Celko’s and Vadim Tropashko’s introductory
articles.

i am guessing that there is no drop in method of using this with
active_scaffold… correct?

Probably. But parent_id shouldn’t present much trouble with
ActiveScaffold.

anyway…

this looks great!

thanks!

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

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