class ActiveRecord::Reflection::AssociationReflection

+has_and_belongs_to_many+, +false+ otherwise.
association. Returns +true+ if the +macro+ is one of +has_many+ or
Returns whether or not this association reflection is for a collection

def collection?
  if @collection.nil?
    @collection = [:has_many, :has_and_belongs_to_many].include?(macro)
  end
  @collection
end