From: Brian Candler <b.candler@...>
Date: 2010-08-03T23:58:38+09:00
Subject: Re: Complex associations

Trish wrote:
> Is there a way to do this?

Named or anonymous scopes perhaps. See these posts:
http://blog.ethanvizitei.com/2009/05/joins-and-namedscopes-in-activerecord.html
http://webjazz.blogspot.com/2008/06/anonymous-scope-unknown-cousin-of-named.html

So I'm guessing something like this (completely untested):

class Store
  def products
    Product.scoped(:joins => :department,
      :conditions=>["products.store_id=? or (products.department_id = 
departments.id and departments.store_id=?)", id, id])
  end
end

And the reverse:

class Product
  def store
    if store_id
      Store.find(store_id)
    elsif department_id
      Store.find_first(:joins => :department,
        :conditions=>["stores.id = departments.store_id and 
departments.id = ?", department_id])
    end
  end
end

I'm not quite sure I've understood the model though. A particular 
product can only be sold in one department or one store? If another 
store wants to stock it as well, do you need another Product row?

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