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copied!<p>Your <code>has_one</code> condition will never work in Rails, as far as I know.</p> <p>You need one explicit <code>has_one</code> or <code>belongs_to</code> or has_many per "link", on both tables. So if you have two "links", you need two <code>has_one</code> and two <code>belongs_to</code>. That is how it works.</p> <p>Secondly, I think you should reconsider your models. The way you are doing it, one person can not be the president of a club and an employee, at the same time. Or be the president of two clubs. Even if you don't have these right now, they can come in the future - it is easier to stay flexible right now.</p> <p>A flexible way of doing this is using a <code>has_many :through</code> with an intermediate table that specifies the role. In other words:</p> <pre><code># The memberships table has a person_id, club_id and role_id, all integers class Membership < ActiveRecord::Base belongs_to :club belongs_to :person validates_presence_of :role_id validates_numericality_of :role_id end class Club < ActiveRecord::Base has_many :memberships, :dependent => :delete_all has_many :people, :through => :memberships end class Person < ActiveRecord::Base has_many :memberships, :dependent => :delete_all has_many :clubs, :through => :memberships end </code></pre> <p>Now, assuming that role_id=0 means employee, role_id=1 means president, and role_id=2 means vice_president, you can use it like this:</p> <pre><code>tyler = Person.find(1) # person_id is 1 other = Person.find(2) # person_id is 2 c = Club.find(1) # club_id is 1 tyler.clubs # returns all the clubs this person is "member" of c.people # returns all the "members" of this club, no matter their role #make tyler the president of c tyler.memberships.create(:club_id => 1, :role_id => 1) #make other the vicepresident of c #but using c.memberships instead of other.memberships (works both ways) c.memberships.create(:person_id => 2, :role_id => 1) #find the (first) president of c c.memberships.find_by_role_id(1).person #find the (first) vicepresident of c c.memberships.find_by_role_id(2).person #find all the employees of c c.memberships.find_all_by_role_id(0).collect { |m| m.person } #find all the clubs of which tyler is president tyler.memberships.find_all_by_role_id(1).collect { |m| m.club } </code></pre> <p>Additional notes:</p> <ul> <li>You could complement this with a roles table and model. Roles would have just a a name, roles would <code>have_many</code> relationships and memberships would <code>belong_to</code> role. Or, you could define methods in memberships for getting the role name (if 0, it returns "employee", if 1, "president", etc</li> <li>You can add validations on memberhips so no more than 1 person can be made president of a given club, or the same employee on the same club twice. Later on, if you start getting "exceptional cases" in which a person needs to be in two places, you will just have to adapt your validations.</li> </ul>

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