How to set foreign key in Rails - ruby-on-rails

Question

I Have a model named employee. The following is my migration file.
class CreateEmployees < ActiveRecord::Migration
def change
create_table :employees, id: false do |t|
t.string :name
t.string :password
t.string :role
t.primary_key :name
end
end
end
Now, I want to create a model named "teamplayer" with the columns as 'name' which needs to refers 'name' column in employee model. And 'tl' column
which is independent to this model. The following is my "teamplayer" migration file.
class CreateTeamplayers < ActiveRecord::Migration
def change
create_table :teamplayers, :id false do |t|
t.string :tl
t.string :name
end
end
end
In the above file, how to reference 'name' column to the model employee? So how to achieve foreign key in rails.

Answer 1

I think you want to look into Active Record Associations (http://guides.rubyonrails.org/association_basics.html)
I know you've asked to create a foreign key on name but unless you plan to ensure that name is unique, then this is possibly not the best plan (depending on the actual relationship you are trying to model - one to many / one to one etc).
I would be tempted to set up the foreign key relationship on employees.id. To do this, you can use the has_many and belongs_to associations.
You could change your teamplayers migration as follows:
class CreateTeamplayers < ActiveRecord::Migration
def change
create_table :teamplayers, :id false do |t|
t.belongs_to :employee
t.string :tl
end
end
end
Then in your Employee model, you can add the has_many side of things:
class Employee < ActiveRecord::Base
has_many :teamplayers
end
You can still easily get the Employee name given a Team Player record with a simple join.
Edit - to get the Employee, you can do something like this, assuming #tis a teamplayer instance:
#t.employee.name
(the code is untested and from memory so....)

Answer 2

You can do it in the teamplayer model, you just need to add index in your migration
class CreateTeamplayers < ActiveRecord::Migration
def change
create_table :teamplayers, :id false do |t|
t.string :tl
t.string :name
end
add_index :teamplayers, :name
end
end
You can set name as Primary key inside the employee model like this
class Employee < ActiveRecord::Base
self.primary_key = "name"
has_many :teamplayers
end
Now inside the model Teamplayer you can set the foreign key
class Teamplayer < ActiveRecord::Base
belongs_to :employee, foreign_key: 'name'
end
This should reference 'name' to employee model