class ActiveFedora::Associations::CollectionProxy

def length

# ]
# #
# #,
# #,
# => [
person.pets
# call the collection with no additional queries:
# Because the collection is loaded, you can

# queries solr for the number of matching records where "person_id_ssi" = 1
person.pets.length # => 3

end
has_many :pets
class Person < ActiveFedora::Base

method will take one less query. Otherwise +size+ is more efficient.
equivalent. If not and you are going to need the records anyway this
If the collection has been already loaded, +length+ and +size+ are
Returns the size of the collection calling +size+ on the target. 
def length
  @association.length
end