Rails - May 2008 - IS A relationship in rails and additional field in Join tabl

Hello,
   I have a couple of questions:
1. How to implement IS A relationship

    I have an events table and model
              person table and model
Now events contain speakers and speakers are people.
So how to implement is a relationship, like speaker IS A person
I DO NOT have speaker table and model. Is there a need to create it.

2. For the time being, I have defined has_many :through relationship
between people and events. In the join table I want to store the TOPIC
that the speaker will speak in the event. So how can i store it from the
form.

so the join table should look like
person_id     event_id     Topic
Thank you.
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

The answer depends on whether or not ''speaker'' is a special
kind of
person that has certain attributes and abilities that only a speaker
has.  If that is the case then you can subclass using Single Table
Inheritance by adding a ''type'' column to your people table and
implementing the Speaker class like this:

class Person < ActiveRecord::Base
  ..general person kinds of things...
end

class Speaker < Person
   ...special speaker stuff...
end

The "<" in the class definition indicates it''s
inheritance.  And, yes,
that means Person IS A extension of the ActiveRecord::Base class.

Now, if your intention is only to say "the speaker at this event is
that particular person over there" then you can do this:

class Event < ARec::Base
  belongs_to :speaker, :class_name=>''Person''
end

As show you''ll need a ''speaker_id'' column on the
event.  You could
also make it ''person_id'' if you prefer, but you''ll
need to
add :foreign_key=>''person_id'' to the belongs_to invocation.
Either
way, this means you can call the person associated with the event the
''speaker'' in the context of the Event.

On May 20, 11:02 am, Ank Ag
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Hello,
>    I have a couple of questions:
> 1. How to implement IS A relationship
>
>     I have an events table and model
>               person table and model
> Now events contain speakers and speakers are people.
> So how to implement is a relationship, like speaker IS A person
> I DO NOT have speaker table and model. Is there a need to create it.
>
> 2. For the time being, I have defined has_many :through relationship
> between people and events. In the join table I want to store the TOPIC
> that the speaker will speak in the event. So how can i store it from the
> form.
>
> so the join table should look like
> person_id     event_id     Topic
> Thank you.
> --
> Posted viahttp://www.ruby-forum.com/.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---