Question

I’m working on a site which has members. Each member has a subscription. For a subscription a member needs to choose a plan of which there are 3.

Is this correct way to do the association

class Member < ActiveRecord::Base
    has_one :plan, :through => :subscription
end

class Subscription < ActiveRecord::Base
    belongs_to :member
    has_many :plans
end

class Plan < ActiveRecord::Base
    belongs_to :subscription
end

Then maybe something like this

member.plan

would be the plan a member is subscribed to.

Answer 1

If a member can belong to one plan at a time you can redo your models as follows:

class Member < ActiveRecord::Base
  has_one :subscription
  has_one :plan, :through => :subscription
end

class Subscription < ActiveRecord::Base
  belongs_to :member
  belongs_to :plan
end

class Plan < ActiveRecord::Base
  belongs_to :subscription
  has_many   :members    
end

Other solution is to avoid the Subscription model altogether by adding a plan_id column to members table.

# has a column called plan_id
class Member < ActiveRecord::Base
  has_one :plan
end

class Plan < ActiveRecord::Base
  has_many   :members    
end