# Data structure for "linked list" **URL:** \ **Category:** Rails\ **Created:** [April 1, 2009, 8:04pm UTC](https://www.ruby-forum.com/t/data-structure-for-linked-list/164476 "2009-04-01T20:04:06Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![jack](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/cc9497/32.png) [@jack](https://www.ruby-forum.com/u/jack)\ **Post date:** [April 1, 2009, 8:04pm UTC](https://www.ruby-forum.com/t/data-structure-for-linked-list/164476/1 "2009-04-01T20:04:06Z")
Folks, I’m trying to figure out the best approach to creating a linked list conceptually in RoR. This is what I’m looking at doing and want to know if there is a best practice approach to this already (my search didn’t seem to indicate this) OR if I’m completely off base on the naming convention I’m using: category table id name categories\_categories table (not defined as a model; should it be?) id category\_id parent\_category\_id Then I should be able to do things like this… Fruit -\> Berry -\> Blueberry Fruit -\> Berry -\> Raspberry Fruit -\> Apple -\> Rome Food -\> Fruit Food -\> Beverage etc. where I create these by recursively(?) accessing the categories\_categories data joined to the category data. The start of a category will be implied where parent\_category\_id is 0. And those parent records could be a foreign key like so categories\_categories\_object table object\_id categories\_categories\_id where object is the other model/table in the many-to-many relationship. Is this the appropriate way to do something like this? If not, could someone point me to some documentation or an example of how I should be handling this. Thanks, Jack ---
**Author:** ![jack](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/cc9497/32.png) [@jack](https://www.ruby-forum.com/u/jack)\ **Post date:** [April 1, 2009, 10:20pm UTC](https://www.ruby-forum.com/t/data-structure-for-linked-list/164476/2 "2009-04-01T22:20:21Z")
I just found some info in the Agile Rails book and with a bit more searching I discovered I could look into one of these: acts\_as\_list acts\_as\_tree acts\_as\_nested I don’t think the list feature works since I’m looking at a hierarchy and want to be able to re-use the same term in different levels. Can acts\_as\_tree allow for multiple trees? i.e. more than one NULL parent\_id? This also seems to imply that I do want to make my categories\_categories table a full blown model, with a better name of course. Could someone confirm I’m on the right track? Thanks, Jack ---
**Author:** ![jack](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/cc9497/32.png) [@jack](https://www.ruby-forum.com/u/jack)\ **Post date:** [April 1, 2009, 11:22pm UTC](https://www.ruby-forum.com/t/data-structure-for-linked-list/164476/3 "2009-04-01T23:22:13Z")
On Wed, Apr 1, 2009 at 1:03 PM, Jack [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I’m trying to figure out the best approach to creating a linked list > conceptually in RoR. [http://www.koders.com/ruby/fidCB5A463AB556F4FFD20E03139FF59563B118D108.aspx?s=socket](http://www.koders.com/ruby/fidCB5A463AB556F4FFD20E03139FF59563B118D108.aspx?s=socket) – Greg D. [http://destiney.com/](http://destiney.com/) ---
**Author:** ![jack](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/cc9497/32.png) [@jack](https://www.ruby-forum.com/u/jack)\ **Post date:** [April 2, 2009, 6:03am UTC](https://www.ruby-forum.com/t/data-structure-for-linked-list/164476/4 "2009-04-02T06:03:48Z")
Jack wrote: > Folks, > > I’m trying to figure out the best approach to creating a linked list > conceptually in RoR. > […] What you describe is a tree, not really a linked list. You could use acts\_as\_tree for this, but you’ll probably get better results with awesome\_nested\_set or something similar. ## Best, Marnen Laibow-Koser removed\_email\_address@domain.invalid [http://www.marnen.org](http://www.marnen.org)