ActiveRecord : Cannot modify association because it goes through more than one other association

Question

I'm not sure why this association is invalid

class Tag < ActiveRecord::Base
  has_and_belongs_to_many :routes
end

class Route < ActiveRecord::Base
 belongs_to :super_route
 has_and_belongs_to_many :tags
end

class SuperRoute < ActiveRecord::Base
  has_one :route
  has_many :tags, through: :route
end

Then I'd expect to be able to do the following

s = SuperRoute.create
s.route = Route.create
s.tags << Tag.create

except this throws the error

ActiveRecord::HasManyThroughNestedAssociationsAreReadonly: Cannot modify association 'SuperRoute#tags' because it goes through more than one other association.

What is the fundamental error here?

Answer 1

class SuperRoute < ActiveRecord::Base
  has_one :route
  has_many :tags     #remove through: :route
end