Association headaches

rubyonrails-talk
1

Hi,

I'm trying to wrap my head around an association problem.

     create_table :events do |t|        t.column :name, :text        t.column :place, :text      end

    create_table :users do |t|        t.column :name, :text     end

    create_table :events_users do |t|        t.column :event_id, :integer        t.column :user_id, :integer        t.column :user_role, :text      end

I want to use :events_users as a HABTM table to connect :events and :users like so:

class Event < ActiveRecord::Base    has_and_belongs_to_many :users end

class User < ActiveRecord::Base    has_and_belongs_to_many :events end

But I also want to be able to access the extra information of which role the user had during an event. I can't see how to do that. has_many :through doesn't seem to offer a solution either, or does it?

Best, Dav

2

So I figure I might create a new class inheriting from User and add some extra variables like:

class Participant < User     @role = ... end

But how can I populate a single extra variable this way? Any suggestions please, still trying to figure Rails out...

Chrs, Dav

3

    create_table :events do |t|       t.column :name, :text       t.column :place, :text     end

   create_table :users do |t|       t.column :name, :text    end

   create_table :events_users do |t|       t.column :event_id, :integer       t.column :user_id, :integer       t.column :user_role, :text     end

I got my HABTM association between users and events going so far, I can even retrieve the records from the database including the extra information from the HABTM table.

event.users #=> <User @attributes={"name"=>"Dav", "user_role"=>"Host"} > etc...

The user_role being selected with the rest of the user attributes seems to be a side-effect of ActiveRecord selecting * from all tables when retrieving HABTM associations. Good so far, but how can I get the user_role value *into* the table? I guess I could specify a custom :insert_sql string in the model, but that seems very messy and additionally I wouldn't know how to hand the attribute to ActiveRecord.

event.users.create(:name => "foo", :user_role => "Guest") certainly wouldn't work...

Any suggestions please! Chrs, Dav

4

You need to use has_many :through.

5

I see! It actually works now. :slight_smile: Thanks!