parent_and_child.rb

# Ok, this is just a simplified example:

@parent.children.all_passing? # => true or false


# I want a method that returns something based on the collection of
# associated objects. Using association extensions, I can put a 
# method on the has_many in parent model:

class Parent < ActiveRecord::Base
  has_many  :children do
    def all_passing?( date )
      proxy_target.all?{ |child| child.average_score > 50 }
    end
  end
end



# However, I think this definition belongs on the child model,
# in case the child model is associated to other models,
# the other associations should also have this method.
# Here it's a simple belongs_to, but is there a way to move the
# above method definition to this side of the association?

class Child < ActiveRecord::Base
  belongs_to :parent
end