How do I link several elements of different types to one another in RoR?

Question

I have Events, Documents, and Surveys which all need to be able to link to one another, I was planning on having a linking table with four columns as follows:

link_elements{
  element1_type CHAR(1)
  element1_id INTEGER
  element2_type CHAR(1)
  element2_id INTEGER
}

The problem is I can't figure out how to make the model in RoR so that I can use the element type field to identify which table the corresponding element id belongs to (Documents, Events, or Surveys). I'm really new to Ruby and any help would really be appreciated.

Answer 1

I think you're just looking for the has_many and belongs_to associations.

If you have an Event model, a Document model, and a Survey model, then you can specify in their respective .rb files in the Models folder if they have or belong to the other models.

Ex: you want Surveys to belong to Documents. In Survey.rb, add the line belongs_to :document. In Document.rb, add the line has_many :surveys.

Now if you add a new "document_id" column in the Surveys table, it will look for a a Document object that corresponds to the id integer in that column.

For more info check out the Rails API.