# How do i model this in Rails? (put down java equivalent design) **URL:** \ **Category:** Rails\ **Created:** [June 7, 2009, 4:30am UTC](https://www.ruby-forum.com/t/how-do-i-model-this-in-rails-put-down-java-equivalent-design/169691 "2009-06-07T04:30:11Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Ritvvij](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/bbce88/32.png) [@Ritvvij](https://www.ruby-forum.com/u/Ritvvij)\ **Post date:** [June 7, 2009, 4:30am UTC](https://www.ruby-forum.com/t/how-do-i-model-this-in-rails-put-down-java-equivalent-design/169691/1 "2009-06-07T04:30:11Z")
Hello guys, Need help!! Finding it hard to model the ‘model’ 😛 within the given rails associations. In java terms, my requirements are… There are 3 entities - module, chapter and activity. Chapter entity is a specilization of Module entity (inheritence) Activity entity is a specialization of Module entity (inheritence) And the tables would have looked like: 1. Module table = Module\_Id, Entity\_type, … 2. Chapter = Chapter\_id, … 3. Activity = Activity\_id, … Hence, if I create a chapter then the tables would be populated as: Module table = Module\_Id, Entity\_type, … = values ( 100, chapter , … ) Chapter table = chapter\_id, … = values ( 100, … ) Basically, the ids of chapter and module would be same and module table would store the type. Now, if I create a activity then the tables would be populated as: Module table = Module\_Id, Entity\_type, … = values ( 101, activity , … ) Activity table = activity\_id, … = values ( 100, … ) Basically, the ids of activity and module would be same and module table would store the type. Can you please guide me how I can model it similarly in rails 2.3.2? Thanks in advance Ritvvij Parrilkh ---
**Author:** ![Ritvvij](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/bbce88/32.png) [@Ritvvij](https://www.ruby-forum.com/u/Ritvvij)\ **Post date:** [June 7, 2009, 9:13am UTC](https://www.ruby-forum.com/t/how-do-i-model-this-in-rails-put-down-java-equivalent-design/169691/2 "2009-06-07T09:13:50Z")
On Jun 7, 3:29 am, Ritvvij [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Activity entity is a specialization of Module entity (inheritence) > table would store the type. That wouldn’t be the rails way of doing it. In rails you’d probably either use single table inheritance or a polymorphic association. Fred ---
**Author:** ![Ritvvij](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/bbce88/32.png) [@Ritvvij](https://www.ruby-forum.com/u/Ritvvij)\ **Post date:** [June 7, 2009, 5:29pm UTC](https://www.ruby-forum.com/t/how-do-i-model-this-in-rails-put-down-java-equivalent-design/169691/3 "2009-06-07T17:29:16Z")
Does seem to be a bit of repetition in your description but it seems straightforward. You have a Module which has an Entity\_type column Each Module has many Chapters where Chapters has a column named module\_id. Each Chapter has many Activities with similar foreign key constraints or You have one Activities table, in which case you don’t specify a relationship. Once you set up the has\_many and belongs\_to pairs, Rails provides the methods to interact with the data. Checkout some ActiveRecord tutorials like this screencast - [http://www.railsenvy.com/2007/8/8/activerecord-tutorial](http://www.railsenvy.com/2007/8/8/activerecord-tutorial) ---
**Author:** ![Ritvvij](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/bbce88/32.png) [@Ritvvij](https://www.ruby-forum.com/u/Ritvvij)\ **Post date:** [June 8, 2009, 6:42pm UTC](https://www.ruby-forum.com/t/how-do-i-model-this-in-rails-put-down-java-equivalent-design/169691/4 "2009-06-08T18:42:57Z")
I’d also chime in that if you create a model named ‘Module’, Rails will most likely break in really interesting ways, as Module is a reserved word in Ruby… –Matt J. On Jun 7, 3:12 am, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)