Association headaches

Rails
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

On 6. Oct 2007, at 14:19, David Zentgraf wrote:

  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.

–
Michael W.

5

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