has_many :through multiple has_one relationships?

Question

I\'m writing a mentorship program for our church in rails (im still farily new to rails)..

And i need to model this..

contact
has_one :father, :class         


        

Answer 1

I totally agree with zetetic. The question looks far more simpler then the answer and there is little we could do about it. I'll add my 20c though.
Tables:

    create_table :contacts do |t|
      t.string :name
      t.string :gender
    end
    create_table :relations, :id => false do |t|
      t.integer :parent_id
      t.integer :child_id
    end

Table relations does not have corresponding model.

class Contact < ActiveRecord::Base
  has_and_belongs_to_many :parents,
    :class_name => 'Contact',
    :join_table => 'relations',
    :foreign_key => 'child_id',
    :association_foreign_key => 'parent_id'

  has_and_belongs_to_many :children,
    :class_name => 'Contact',
    :join_table => 'relations',
    :foreign_key => 'parent_id',
    :association_foreign_key => 'child_id'

  def siblings
    result = self.parents.reduce [] {|children, p| children.concat  p.children}
    result.uniq.reject {|c| c == self}
  end

  def father
    parents.where(:gender => 'm').first
  end

  def mother
    parents.where(:gender => 'f').first
  end
end  

Now we have regular Rails assosiations. So we can

alice.parents << bob
alice.save

bob.chidren << cindy
bob.save

alice.parents.create(Contact.create(:name => 'Teresa', :gender => 'f')

and all stuff like that.