Question

I have Group model that has_many institutions, and schools.

class Group
  has_many :institutions
  has_many :schools
end

However I need my Group to have_and_belongs_to_many :users but I want all the users that are associated through the institutions and schools like this:

class Group
  has_many :institutions
  has_many :users, :through => :instiutions
  has_many :schools
  has_many :users, :through => :schools
end

class School
  belongs_to :group      

  has_many :educations
  has_many :users, :through => :educations
end

class Institution
  belongs_to :group      

  has_many :institutional_educations
  has_many :users, :through => :institutional_educations
end

Obviously this isn’t possible so what should I do?

Answer 1

Just offhand, have you considered using single table inheritance, so that school is a type of institution?

Your School class would inherit from Institution (“class School < Institution”). Plus, I guess you’d call it something else but you could have “class GenericInstitution < Institution” as well. Then your Group class could look like this:

 class Group
  :has_many :school_users, :through => :schools, 
  :has_many :generic_institution_users, :through => :generic_institutions

   # if you need all of the users at once: 
   :has_many :users, :through => :institutions
 end

You’d probably have to specify a foreign key or two to get this to work for you.

Also, I can’t quite figure see what an :institutional_education is, but if you really need it you could do the same thing there (maybe “class institutional_education < education”, or maybe the other way around.