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Tag: v4.1.0.beta1
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require 'active_support/core_ext/array/wrap'
module ActiveRecord
module Associations
# = Active Record Associations
#
# This is the root class of all associations ('+ Foo' signifies an included module Foo):
#
# Association
# SingularAssociation
# HasOneAssociation
# HasOneThroughAssociation + ThroughAssociation
# BelongsToAssociation
# BelongsToPolymorphicAssociation
# CollectionAssociation
# HasManyAssociation
# HasManyThroughAssociation + ThroughAssociation
class Association #:nodoc:
attr_reader :owner, :target, :reflection
attr_accessor :inversed
delegate :options, :to => :reflection
def initialize(owner, reflection)
reflection.check_validity!
@owner, @reflection = owner, reflection
reset
reset_scope
end
# Returns the name of the table of the associated class:
#
# post.comments.aliased_table_name # => "comments"
#
def aliased_table_name
klass.table_name
end
# Resets the \loaded flag to +false+ and sets the \target to +nil+.
def reset
@loaded = false
@target = nil
@stale_state = nil
@inversed = false
end
# Reloads the \target and returns +self+ on success.
def reload
reset
reset_scope
load_target
self unless target.nil?
end
# Has the \target been already \loaded?
def loaded?
@loaded
end
# Asserts the \target has been loaded setting the \loaded flag to +true+.
def loaded!
@loaded = true
@stale_state = stale_state
@inversed = false
end
# The target is stale if the target no longer points to the record(s) that the
# relevant foreign_key(s) refers to. If stale, the association accessor method
# on the owner will reload the target. It's up to subclasses to implement the
# stale_state method if relevant.
#
# Note that if the target has not been loaded, it is not considered stale.
def stale_target?
!inversed && loaded? && @stale_state != stale_state
end
# Sets the target of this association to <tt>\target</tt>, and the \loaded flag to +true+.
def target=(target)
@target = target
loaded!
end
def scope
target_scope.merge(association_scope)
end
# The scope for this association.
#
# Note that the association_scope is merged into the target_scope only when the
# scope method is called. This is because at that point the call may be surrounded
# by scope.scoping { ... } or with_scope { ... } etc, which affects the scope which
# actually gets built.
def association_scope
if klass
@association_scope ||= AssociationScope.new(self).scope
end
end
def reset_scope
@association_scope = nil
end
# Set the inverse association, if possible
def set_inverse_instance(record)
if invertible_for?(record)
inverse = record.association(inverse_reflection_for(record).name)
inverse.target = owner
inverse.inversed = true
end
record
end
# Returns the class of the target. belongs_to polymorphic overrides this to look at the
# polymorphic_type field on the owner.
def klass
reflection.klass
end
# Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the
# through association's scope)
def target_scope
AssociationRelation.create(klass, klass.arel_table, self).merge!(klass.all)
end
# Loads the \target if needed and returns it.
#
# This method is abstract in the sense that it relies on +find_target+,
# which is expected to be provided by descendants.
#
# If the \target is already \loaded it is just returned. Thus, you can call
# +load_target+ unconditionally to get the \target.
#
# ActiveRecord::RecordNotFound is rescued within the method, and it is
# not reraised. The proxy is \reset and +nil+ is the return value.
def load_target
@target = find_target if (@stale_state && stale_target?) || find_target?
loaded! unless loaded?
target
rescue ActiveRecord::RecordNotFound
reset
end
def interpolate(sql, record = nil)
if sql.respond_to?(:to_proc)
owner.instance_exec(record, &sql)
else
sql
end
end
# We can't dump @reflection since it contains the scope proc
def marshal_dump
ivars = (instance_variables - [:@reflection]).map { |name| [name, instance_variable_get(name)] }
[@reflection.name, ivars]
end
def marshal_load(data)
reflection_name, ivars = data
ivars.each { |name, val| instance_variable_set(name, val) }
@reflection = @owner.class.reflect_on_association(reflection_name)
end
def initialize_attributes(record) #:nodoc:
skip_assign = [reflection.foreign_key, reflection.type].compact
attributes = create_scope.except(*(record.changed - skip_assign))
record.assign_attributes(attributes)
set_inverse_instance(record)
end
private
def find_target?
!loaded? && (!owner.new_record? || foreign_key_present?) && klass
end
def creation_attributes
attributes = {}
if (reflection.macro == :has_one || reflection.macro == :has_many) && !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
# Sets the owner attributes on the given record
def set_owner_attributes(record)
creation_attributes.each { |key, value| record[key] = value }
end
# Returns true if there is a foreign key present on the owner which
# references the target. This is used to determine whether we can load
# the target if the owner is currently a new record (and therefore
# without a key). If the owner is a new record then foreign_key must
# be present in order to load target.
#
# Currently implemented by belongs_to (vanilla and polymorphic) and
# has_one/has_many :through associations which go through a belongs_to.
def foreign_key_present?
false
end
# Raises ActiveRecord::AssociationTypeMismatch unless +record+ is of
# the kind of the class of the associated objects. Meant to be used as
# a sanity check when you are about to assign an associated record.
def raise_on_type_mismatch!(record)
unless record.is_a?(reflection.klass) || record.is_a?(reflection.class_name.constantize)
message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
raise ActiveRecord::AssociationTypeMismatch, message
end
end
# Can be redefined by subclasses, notably polymorphic belongs_to
# The record parameter is necessary to support polymorphic inverses as we must check for
# the association in the specific class of the record.
def inverse_reflection_for(record)
reflection.inverse_of
end
# Returns true if inverse association on the given record needs to be set.
# This method is redefined by subclasses.
def invertible_for?(record)
foreign_key_for?(record) && inverse_reflection_for(record)
end
# Returns true if record contains the foreign_key
def foreign_key_for?(record)
record.attributes.has_key? reflection.foreign_key
end
# This should be implemented to return the values of the relevant key(s) on the owner,
# so that when stale_state is different from the value stored on the last find_target,
# the target is stale.
#
# This is only relevant to certain associations, which is why it returns nil by default.
def stale_state
end
def build_record(attributes)
reflection.build_association(attributes) do |record|
initialize_attributes(record)
end
end
end
end
end
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