rails foreign key problem

I am a newbie in the Rails framework. I've created tables:

DealerGroups                      开发者_JS百科   Dealer 
------------                         ------------
Id:integer(primary key)              Id:integer(primary key)
name:string                          dealer_group_id:integer(foreign key)

But when I try to set Dealer.dealer_group_id = value (this value exists in the DealerGroups table) I get an "UninitializedConstant Dealer::DealerGroup" exception.

In models I have :

class Dealer < ActiveRecord::Base
  belongs_to :dealer_buying_group, :foreign_key => "dealer_buying_group"
end

class DealersGroup < ActiveRecord::Base
  has_many :dealer
end

If I delete the has_many and belongs_to relations, it all works fine.

Why won't it work with the relations?

---

Be careful with the "s" (why is your "Dealer" table is not "Dealers"?) You do not need to manually set a foreign key in Rails, all you need to define the Model_ID field to it as you generate your scaffold/model/controller, then belongs_to and has_many in the model will do the relation for you

Database:

DealerGroups                         Dealers 
------------                         ------------
Id:integer(primary key)              Id:integer(primary key)
name:string                          dealergroup_id:integer

Models :

class Dealer < ActiveRecord::Base
  belongs_to :dealergroup
end

class DealersGroup < ActiveRecord::Base
  has_many :dealers
end

To access dealdergroup's name from dealers, just use

controller: 
@dealer = Dealer.find_by_id(myInt)

view:
<%= @dealer.dealergroup.name %>

---

You have class DealersGroup whereas you are looking for dealer_group_id.