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module ActiveRecord
# = Active Record Reflection
module Reflection # :nodoc:
extend ActiveSupport::Concern
included do
class_attribute :reflections
class_attribute :aggregate_reflections
self.reflections = {}
self.aggregate_reflections = {}
end
# \Reflection enables to interrogate Active Record classes and objects
# about their associations and aggregations. This information can,
# for example, be used in a form builder that takes an Active Record object
# and creates input fields for all of the attributes depending on their type
# and displays the associations to other objects.
#
# MacroReflection class has info for AggregateReflection and AssociationReflection
# classes.
module ClassMethods
def create_reflection(macro, name, scope, options, active_record)
case macro
when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
klass = options[:through] ? ThroughReflection : AssociationReflection
when :composed_of
klass = AggregateReflection
end
reflection = klass.new(macro, name, scope, options, active_record)
if klass == AggregateReflection
self.aggregate_reflections = self.aggregate_reflections.merge(name => reflection)
else
self.reflections = self.reflections.merge(name => reflection)
end
reflection
end
# Returns an array of AggregateReflection objects for all the aggregations in the class.
def reflect_on_all_aggregations
aggregate_reflections.values
end
# Returns the AggregateReflection object for the named +aggregation+ (use the symbol).
#
# Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection
#
def reflect_on_aggregation(aggregation)
aggregate_reflections[aggregation]
end
# Returns an array of AssociationReflection objects for all the
# associations in the class. If you only want to reflect on a certain
# association type, pass in the symbol (<tt>:has_many</tt>, <tt>:has_one</tt>,
# <tt>:belongs_to</tt>) as the first parameter.
#
# Example:
#
# Account.reflect_on_all_associations # returns an array of all associations
# Account.reflect_on_all_associations(:has_many) # returns an array of all has_many associations
#
def reflect_on_all_associations(macro = nil)
association_reflections = reflections.values
macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
end
# Returns the AssociationReflection object for the +association+ (use the symbol).
#
# Account.reflect_on_association(:owner) # returns the owner AssociationReflection
# Invoice.reflect_on_association(:line_items).macro # returns :has_many
#
def reflect_on_association(association)
reflections[association]
end
# Returns an array of AssociationReflection objects for all associations which have <tt>:autosave</tt> enabled.
def reflect_on_all_autosave_associations
reflections.values.select { |reflection| reflection.options[:autosave] }
end
end
# Base class for AggregateReflection and AssociationReflection. Objects of
# AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods.
#
# MacroReflection
# AggregateReflection
# AssociationReflection
# ThroughReflection
class MacroReflection
# Returns the name of the macro.
#
# <tt>composed_of :balance, class_name: 'Money'</tt> returns <tt>:balance</tt>
# <tt>has_many :clients</tt> returns <tt>:clients</tt>
attr_reader :name
# Returns the macro type.
#
# <tt>composed_of :balance, class_name: 'Money'</tt> returns <tt>:composed_of</tt>
# <tt>has_many :clients</tt> returns <tt>:has_many</tt>
attr_reader :macro
attr_reader :scope
# Returns the hash of options used for the macro.
#
# <tt>composed_of :balance, class_name: 'Money'</tt> returns <tt>{ class_name: "Money" }</tt>
# <tt>has_many :clients</tt> returns <tt>{}</tt>
attr_reader :options
attr_reader :active_record
attr_reader :plural_name # :nodoc:
def initialize(macro, name, scope, options, active_record)
@macro = macro
@name = name
@scope = scope
@options = options
@active_record = active_record
@plural_name = active_record.pluralize_table_names ?
name.to_s.pluralize : name.to_s
end
def autosave=(autosave)
@automatic_inverse_of = false
@options[:autosave] = autosave
end
# Returns the class for the macro.
#
# <tt>composed_of :balance, class_name: 'Money'</tt> returns the Money class
# <tt>has_many :clients</tt> returns the Client class
def klass
@klass ||= class_name.constantize
end
# Returns the class name for the macro.
#
# <tt>composed_of :balance, class_name: 'Money'</tt> returns <tt>'Money'</tt>
# <tt>has_many :clients</tt> returns <tt>'Client'</tt>
def class_name
@class_name ||= (options[:class_name] || derive_class_name).to_s
end
# Returns +true+ if +self+ and +other_aggregation+ have the same +name+ attribute, +active_record+ attribute,
# and +other_aggregation+ has an options hash assigned to it.
def ==(other_aggregation)
super ||
other_aggregation.kind_of?(self.class) &&
name == other_aggregation.name &&
other_aggregation.options &&
active_record == other_aggregation.active_record
end
private
def derive_class_name
name.to_s.camelize
end
end
# Holds all the meta-data about an aggregation as it was specified in the
# Active Record class.
class AggregateReflection < MacroReflection #:nodoc:
def mapping
mapping = options[:mapping] || [name, name]
mapping.first.is_a?(Array) ? mapping : [mapping]
end
end
# Holds all the meta-data about an association as it was specified in the
# Active Record class.
class AssociationReflection < MacroReflection #:nodoc:
# Returns the target association's class.
#
# class Author < ActiveRecord::Base
# has_many :books
# end
#
# Author.reflect_on_association(:books).klass
# # => Book
#
# <b>Note:</b> Do not call +klass.new+ or +klass.create+ to instantiate
# a new association object. Use +build_association+ or +create_association+
# instead. This allows plugins to hook into association object creation.
def klass
@klass ||= active_record.send(:compute_type, class_name)
end
attr_reader :type, :foreign_type
def initialize(*args)
super
@collection = [:has_many, :has_and_belongs_to_many].include?(macro)
@automatic_inverse_of = nil
@type = options[:as] && "#{options[:as]}_type"
@foreign_type = options[:foreign_type] || "#{name}_type"
end
# Returns a new, unsaved instance of the associated class. +attributes+ will
# be passed to the class's constructor.
def build_association(attributes, &block)
klass.new(attributes, &block)
end
def table_name
klass.table_name
end
def quoted_table_name
klass.quoted_table_name
end
def join_table
@join_table ||= options[:join_table] || derive_join_table
end
def foreign_key
@foreign_key ||= options[:foreign_key] || derive_foreign_key
end
def primary_key_column
klass.columns_hash[klass.primary_key]
end
def association_foreign_key
@association_foreign_key ||= options[:association_foreign_key] || class_name.foreign_key
end
# klass option is necessary to support loading polymorphic associations
def association_primary_key(klass = nil)
options[:primary_key] || primary_key(klass || self.klass)
end
def active_record_primary_key
@active_record_primary_key ||= options[:primary_key] || primary_key(active_record)
end
def counter_cache_column
if options[:counter_cache] == true
"#{active_record.name.demodulize.underscore.pluralize}_count"
elsif options[:counter_cache]
options[:counter_cache].to_s
end
end
def check_validity!
check_validity_of_inverse!
if has_and_belongs_to_many? && association_foreign_key == foreign_key
raise HasAndBelongsToManyAssociationForeignKeyNeeded.new(self)
end
end
def check_validity_of_inverse!
unless options[:polymorphic]
if has_inverse? && inverse_of.nil?
raise InverseOfAssociationNotFoundError.new(self)
end
end
end
def through_reflection
nil
end
def source_reflection
nil
end
# A chain of reflections from this one back to the owner. For more see the explanation in
# ThroughReflection.
def chain
[self]
end
def nested?
false
end
# An array of arrays of scopes. Each item in the outside array corresponds to a reflection
# in the #chain.
def scope_chain
scope ? [[scope]] : [[]]
end
alias :source_macro :macro
def has_inverse?
inverse_name
end
def inverse_of
return unless inverse_name
@inverse_of ||= klass.reflect_on_association inverse_name
end
def polymorphic_inverse_of(associated_class)
if has_inverse?
if inverse_relationship = associated_class.reflect_on_association(options[:inverse_of])
inverse_relationship
else
raise InverseOfAssociationNotFoundError.new(self, associated_class)
end
end
end
# Returns whether or not this association reflection is for a collection
# association. Returns +true+ if the +macro+ is either +has_many+ or
# +has_and_belongs_to_many+, +false+ otherwise.
def collection?
@collection
end
# Returns whether or not the association should be validated as part of
# the parent's validation.
#
# Unless you explicitly disable validation with
# <tt>validate: false</tt>, validation will take place when:
#
# * you explicitly enable validation; <tt>validate: true</tt>
# * you use autosave; <tt>autosave: true</tt>
# * the association is a +has_many+ association
def validate?
!options[:validate].nil? ? options[:validate] : (options[:autosave] == true || macro == :has_many)
end
# Returns +true+ if +self+ is a +belongs_to+ reflection.
def belongs_to?
macro == :belongs_to
end
def has_and_belongs_to_many?
macro == :has_and_belongs_to_many
end
def association_class
case macro
when :belongs_to
if options[:polymorphic]
Associations::BelongsToPolymorphicAssociation
else
Associations::BelongsToAssociation
end
when :has_and_belongs_to_many
Associations::HasAndBelongsToManyAssociation
when :has_many
if options[:through]
Associations::HasManyThroughAssociation
else
Associations::HasManyAssociation
end
when :has_one
if options[:through]
Associations::HasOneThroughAssociation
else
Associations::HasOneAssociation
end
end
end
def polymorphic?
options.key? :polymorphic
end
VALID_AUTOMATIC_INVERSE_MACROS = [:has_many, :has_one, :belongs_to]
INVALID_AUTOMATIC_INVERSE_OPTIONS = [:conditions, :through, :polymorphic, :foreign_key]
private
# Attempts to find the inverse association name automatically.
# If it cannot find a suitable inverse association name, it returns
# nil.
def inverse_name
options.fetch(:inverse_of) do
if @automatic_inverse_of == false
nil
else
@automatic_inverse_of ||= automatic_inverse_of
end
end
end
# returns either nil or the inverse association name that it finds.
def automatic_inverse_of
if can_find_inverse_of_automatically?(self)
inverse_name = active_record.name.downcase.to_sym
begin
reflection = klass.reflect_on_association(inverse_name)
rescue NameError
# Give up: we couldn't compute the klass type so we won't be able
# to find any associations either.
reflection = false
end
if valid_inverse_reflection?(reflection)
return inverse_name
end
end
false
end
# Checks if the inverse reflection that is returned from the
# +set_automatic_inverse_of+ method is a valid reflection. We must
# make sure that the reflection's active_record name matches up
# with the current reflection's klass name.
#
# Note: klass will always be valid because when there's a NameError
# from calling +klass+, +reflection+ will already be set to false.
def valid_inverse_reflection?(reflection)
reflection &&
klass.name == reflection.active_record.name &&
klass.primary_key == reflection.active_record_primary_key &&
can_find_inverse_of_automatically?(reflection)
end
# Checks to see if the reflection doesn't have any options that prevent
# us from being able to guess the inverse automatically. First, the
# <tt>inverse_of</tt> option cannot be set to false. Second, we must
# have <tt>has_many</tt>, <tt>has_one</tt>, <tt>belongs_to</tt> associations.
# Third, we must not have options such as <tt>:polymorphic</tt> or
# <tt>:foreign_key</tt> which prevent us from correctly guessing the
# inverse association.
#
# Anything with a scope can additionally ruin our attempt at finding an
# inverse, so we exclude reflections with scopes.
def can_find_inverse_of_automatically?(reflection)
reflection.options[:inverse_of] != false &&
VALID_AUTOMATIC_INVERSE_MACROS.include?(reflection.macro) &&
!INVALID_AUTOMATIC_INVERSE_OPTIONS.any? { |opt| reflection.options[opt] } &&
!reflection.scope
end
def derive_class_name
class_name = name.to_s.camelize
class_name = class_name.singularize if collection?
class_name
end
def derive_foreign_key
if belongs_to?
"#{name}_id"
elsif options[:as]
"#{options[:as]}_id"
else
active_record.name.foreign_key
end
end
def derive_join_table
[active_record.table_name, klass.table_name].sort.join("\0").gsub(/^(.*_)(.+)\0\1(.+)/, '\1\2_\3').gsub("\0", "_")
end
def primary_key(klass)
klass.primary_key || raise(UnknownPrimaryKey.new(klass))
end
end
# Holds all the meta-data about a :through association as it was specified
# in the Active Record class.
class ThroughReflection < AssociationReflection #:nodoc:
delegate :foreign_key, :foreign_type, :association_foreign_key,
:active_record_primary_key, :type, :to => :source_reflection
def initialize(macro, name, scope, options, active_record)
super
@source_reflection_name = options[:source]
end
# Returns the source of the through reflection. It checks both a singularized
# and pluralized form for <tt>:belongs_to</tt> or <tt>:has_many</tt>.
#
# class Post < ActiveRecord::Base
# has_many :taggings
# has_many :tags, through: :taggings
# end
#
# class Tagging < ActiveRecord::Base
# belongs_to :post
# belongs_to :tag
# end
#
# tags_reflection = Post.reflect_on_association(:tags)
# tags_reflection.source_reflection
# # => <ActiveRecord::Reflection::AssociationReflection: @macro=:belongs_to, @name=:tag, @active_record=Tagging, @plural_name="tags">
#
def source_reflection
through_reflection.klass.reflect_on_association(source_reflection_name)
end
# Returns the AssociationReflection object specified in the <tt>:through</tt> option
# of a HasManyThrough or HasOneThrough association.
#
# class Post < ActiveRecord::Base
# has_many :taggings
# has_many :tags, through: :taggings
# end
#
# tags_reflection = Post.reflect_on_association(:tags)
# tags_reflection.through_reflection
# # => <ActiveRecord::Reflection::AssociationReflection: @macro=:has_many, @name=:taggings, @active_record=Post, @plural_name="taggings">
#
def through_reflection
active_record.reflect_on_association(options[:through])
end
# Returns an array of reflections which are involved in this association. Each item in the
# array corresponds to a table which will be part of the query for this association.
#
# The chain is built by recursively calling #chain on the source reflection and the through
# reflection. The base case for the recursion is a normal association, which just returns
# [self] as its #chain.
#
# class Post < ActiveRecord::Base
# has_many :taggings
# has_many :tags, through: :taggings
# end
#
# tags_reflection = Post.reflect_on_association(:tags)
# tags_reflection.chain
# # => [<ActiveRecord::Reflection::ThroughReflection: @macro=:has_many, @name=:tags, @options={:through=>:taggings}, @active_record=Post>,
# <ActiveRecord::Reflection::AssociationReflection: @macro=:has_many, @name=:taggings, @options={}, @active_record=Post>]
#
def chain
@chain ||= begin
chain = source_reflection.chain + through_reflection.chain
chain[0] = self # Use self so we don't lose the information from :source_type
chain
end
end
# Consider the following example:
#
# class Person
# has_many :articles
# has_many :comment_tags, through: :articles
# end
#
# class Article
# has_many :comments
# has_many :comment_tags, through: :comments, source: :tags
# end
#
# class Comment
# has_many :tags
# end
#
# There may be scopes on Person.comment_tags, Article.comment_tags and/or Comment.tags,
# but only Comment.tags will be represented in the #chain. So this method creates an array
# of scopes corresponding to the chain.
def scope_chain
@scope_chain ||= begin
scope_chain = source_reflection.scope_chain.map(&:dup)
# Add to it the scope from this reflection (if any)
scope_chain.first << scope if scope
through_scope_chain = through_reflection.scope_chain
if options[:source_type]
through_scope_chain.first <<
through_reflection.klass.where(foreign_type => options[:source_type])
end
# Recursively fill out the rest of the array from the through reflection
scope_chain + through_scope_chain
end
end
# The macro used by the source association
def source_macro
source_reflection.source_macro
end
# A through association is nested if there would be more than one join table
def nested?
chain.length > 2 || through_reflection.macro == :has_and_belongs_to_many
end
# We want to use the klass from this reflection, rather than just delegate straight to
# the source_reflection, because the source_reflection may be polymorphic. We still
# need to respect the source_reflection's :primary_key option, though.
def association_primary_key(klass = nil)
# Get the "actual" source reflection if the immediate source reflection has a
# source reflection itself
source_reflection = self.source_reflection
while source_reflection.source_reflection
source_reflection = source_reflection.source_reflection
end
source_reflection.options[:primary_key] || primary_key(klass || self.klass)
end
# Gets an array of possible <tt>:through</tt> source reflection names in both singular and plural form.
#
# class Post < ActiveRecord::Base
# has_many :taggings
# has_many :tags, through: :taggings
# end
#
# tags_reflection = Post.reflect_on_association(:tags)
# tags_reflection.source_reflection_names
# # => [:tag, :tags]
#
def source_reflection_names
(options[:source] ? [options[:source]] : [name.to_s.singularize, name]).collect { |n| n.to_sym }.uniq
end
def source_reflection_name # :nodoc:
return @source_reflection_name if @source_reflection_name
names = [name.to_s.singularize, name].collect { |n| n.to_sym }.uniq
names = names.find_all { |n|
through_reflection.klass.reflect_on_association(n)
}
if names.length > 1
example_options = options.dup
example_options[:source] = source_reflection_names.first
ActiveSupport::Deprecation.warn <<-eowarn
Ambiguous source reflection for through association. Please specify a :source
directive on your declaration like:
class #{active_record.name} < ActiveRecord::Base
#{macro} :#{name}, #{example_options}
end
eowarn
end
@source_reflection_name = names.first
end
def source_options
source_reflection.options
end
def through_options
through_reflection.options
end
def check_validity!
if through_reflection.nil?
raise HasManyThroughAssociationNotFoundError.new(active_record.name, self)
end
if through_reflection.options[:polymorphic]
raise HasManyThroughAssociationPolymorphicThroughError.new(active_record.name, self)
end
if source_reflection.nil?
raise HasManyThroughSourceAssociationNotFoundError.new(self)
end
if options[:source_type] && source_reflection.options[:polymorphic].nil?
raise HasManyThroughAssociationPointlessSourceTypeError.new(active_record.name, self, source_reflection)
end
if source_reflection.options[:polymorphic] && options[:source_type].nil?
raise HasManyThroughAssociationPolymorphicSourceError.new(active_record.name, self, source_reflection)
end
if macro == :has_one && through_reflection.collection?
raise HasOneThroughCantAssociateThroughCollection.new(active_record.name, self, through_reflection)
end
check_validity_of_inverse!
end
private
def derive_class_name
# get the class_name of the belongs_to association of the through reflection
options[:source_type] || source_reflection.class_name
end
end
end
end
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