class ActiveFedora::Associations::Association


HasManyAssociation
AssociationCollection
BelongsToAssociation
Association
This is the root class of all associations:

def association_scope

actually gets built.
by scope.scoping { ... } or with_scope { ... } etc, which affects the scope which
scope method is called. This is because at that point the call may be surrounded
Note that the association_scope is merged into the target_scope only when the

The scope for this association. 
def association_scope
  @association_scope ||= AssociationScope.scope(self) if klass
end

def build_record(attributes) 

def build_record(attributes)
  reflection.build_association(attributes) do |record|
    initialize_attributes(record)
  end
end

def creation_attributes 

def creation_attributes
  attributes = {}
  if (reflection.has_one? || reflection.collection?) && !options[:through]
    attributes[reflection.foreign_key] = owner[reflection.active_record_primary_key]
    if reflection.options[:as]
      attributes[reflection.type] = owner.class.base_class.name
    end
  end
  attributes
end

def find_target? 

def find_target?
  !loaded? && (!owner.new_record? || foreign_key_present?) && klass
end

def foreign_key_present?

Currently implemented by belongs_to

be present in order to load target.
without a key). If the owner is a new record then foreign_key must
the target if the owner is currently a new record (and therefore
references the target. This is used to determine whether we can load
Returns true if there is a foreign key present on the owner which 
def foreign_key_present?
  false
end

def initialize(owner, reflection) 

def initialize(owner, reflection)
  reflection.check_validity!
  @owner = owner
  @reflection = reflection
  reset
  reset_scope
end

def initialize_attributes(record, except_from_scope_attributes = nil) #:nodoc:

:nodoc: 
def initialize_attributes(record, except_from_scope_attributes = nil) #:nodoc:
  except_from_scope_attributes ||= {}
  skip_assign = [reflection.foreign_key].compact
  assigned_keys = record.changed
  assigned_keys += except_from_scope_attributes.keys.map(&:to_s)
  attributes = create_scope.except(*(assigned_keys - skip_assign))
  record.assign_attributes(attributes)
  set_inverse_instance(record)
end

def inverse_reflection_for(_record)

the association in the specific class of the record.
The record parameter is necessary to support polymorphic inverses as we must check for
Can be redefined by subclasses, notably polymorphic belongs_to 
def inverse_reflection_for(_record)
  reflection.inverse_of
end

def invertible_for?(record)

This method is redefined by subclasses.
Returns true if inverse association on the given record needs to be set. 
def invertible_for?(record)
  inverse_reflection_for(record)
end

def load_target

not reraised. The proxy is \reset and +nil+ is the return value.
ActiveFedora::ObjectNotFoundError is rescued within the method, and it is

+load_target+ unconditionally to get the \target.
If the \target is already \loaded it is just returned. Thus, you can call

which is expected to be provided by descendants.
This method is abstract in the sense that it relies on +find_target+,

Loads the \target if needed and returns it. 
def load_target
  @target = find_target if (@stale_state && stale_target?) || find_target?
  loaded! unless loaded?
  target
rescue ActiveFedora::ObjectNotFoundError
  reset
end

def loaded!

Asserts the \target has been loaded setting the \loaded flag to +true+. 
def loaded!
  @loaded = true
  @stale_state = stale_state
  @inversed = false
end

def loaded?

Has the \target been already \loaded? 
def loaded?
  @loaded
end

def raise_on_type_mismatch!(record)

a sanity check when you are about to assign an associated record.
the kind of the class of the associated objects. Meant to be used as
Raises ActiveFedora::AssociationTypeMismatch unless +record+ is of 
def raise_on_type_mismatch!(record)
  unless record.is_a?(reflection.klass)
    fresh_class = reflection.class_name.safe_constantize
    unless fresh_class && record.is_a?(fresh_class)
      message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
      raise ActiveFedora::AssociationTypeMismatch, message
    end
  end
  type_validator.validate!(self, record)
end

def reload

Reloads the \target and returns +self+ on success. 
def reload
  reset
  reset_scope
  load_target
  self unless @target.nil?
end

def reset

Resets the \loaded flag to +false+ and sets the \target to +nil+. 
def reset
  @loaded = false
  @target = nil
  @stale_state = nil
  @inversed = false
end

def reset_scope 

def reset_scope
  @association_scope = nil
end

def scope 

def scope
  target_scope.merge(association_scope)
end

def set_inverse_instance(record)

Set the inverse association, if possible 
def set_inverse_instance(record)
  return unless record && invertible_for?(record)
  inverse = record.association(inverse_reflection_for(record).name.to_sym)
  if inverse.is_a? ActiveFedora::Associations::HasAndBelongsToManyAssociation
    inverse.target << owner
  else
    inverse.target = owner
  end
  inverse.inversed = true
end

def set_owner_attributes(record)

Sets the owner attributes on the given record 
def set_owner_attributes(record)
  creation_attributes.each { |key, value| record[key] = value }
end

def stale_state

This is only relevant to certain associations, which is why it returns nil by default.

the target is stale.
so that when state_state is different from the value stored on the last find_target,
This should be implemented to return the values of the relevant key(s) on the owner, 
def stale_state
end

def stale_target?

Note that if the target has not been loaded, it is not considered stale.

state_state method if relevant.
on the owner will reload the target. It's up to subclasses to implement the
relevant foreign_key(s) refers to. If stale, the association accessor method
The target is stale if the target no longer points to the record(s) that the 
def stale_target?
  !inversed && loaded? && @stale_state != stale_state
end

def target=(target)

Sets the target of this proxy to \target, and the \loaded flag to +true+. 
def target=(target)
  @target = target
  loaded!
end

def target_scope

through association's scope)
Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the 
def target_scope
  klass.all
end

def type_validator 

def type_validator
  options[:type_validator] || NullValidator
end