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module ActiveRecord
module Reflection # :nodoc:
def self.append_features(base)
super
base.extend(ClassMethods)
base.class_eval do
class << self
alias_method :composed_of_without_reflection, :composed_of
def composed_of_with_reflection(part_id, options = {})
composed_of_without_reflection(part_id, options)
reflect_on_all_aggregations << AggregateReflection.new(:composed_of, part_id, options, self)
end
alias_method :composed_of, :composed_of_with_reflection
end
end
for association_type in %w( belongs_to has_one has_many has_and_belongs_to_many )
base.module_eval <<-"end_eval"
class << self
alias_method :#{association_type}_without_reflection, :#{association_type}
def #{association_type}_with_reflection(association_id, options = {}, &block)
#{association_type}_without_reflection(association_id, options, &block)
reflect_on_all_associations << AssociationReflection.new(:#{association_type}, association_id, options, self)
end
alias_method :#{association_type}, :#{association_type}_with_reflection
end
end_eval
end
end
# Reflection allows you to interrogate Active Record classes and objects about their associations and aggregations.
# This information can, for example, be used in a form builder that took an Active Record object and created input
# fields for all of the attributes depending on their type and displayed the associations to other objects.
#
# You can find the interface for the AggregateReflection and AssociationReflection classes in the abstract MacroReflection class.
module ClassMethods
# Returns an array of AggregateReflection objects for all the aggregations in the class.
def reflect_on_all_aggregations
read_inheritable_attribute(:aggregations) or write_inheritable_attribute(:aggregations, [])
end
# Returns the AggregateReflection object for the named +aggregation+ (use the symbol). Example:
# Account.reflect_on_aggregation(:balance) # returns the balance AggregateReflection
def reflect_on_aggregation(aggregation)
reflect_on_all_aggregations.find { |reflection| reflection.name == aggregation } unless reflect_on_all_aggregations.nil?
end
# Returns an array of AssociationReflection objects for all the aggregations in the class.
def reflect_on_all_associations
read_inheritable_attribute(:associations) or write_inheritable_attribute(:associations, [])
end
# Returns the AssociationReflection object for the named +aggregation+ (use the symbol). Example:
# Account.reflect_on_association(:owner) # returns the owner AssociationReflection
def reflect_on_association(association)
reflect_on_all_associations.find { |reflection| reflection.name == association }
end
end
# Abstract base class for AggregateReflection and AssociationReflection that describes the interface available for both of
# those classes. Objects of AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods.
class MacroReflection
attr_reader :active_record
def initialize(macro, name, options, active_record)
@macro, @name, @options, @active_record = macro, name, options, active_record
end
# Returns the name of the macro, so it would return :balance for "composed_of :balance, :class_name => 'Money'" or
# :clients for "has_many :clients".
def name
@name
end
# Returns the name of the macro, so it would return :composed_of for
# "composed_of :balance, :class_name => 'Money'" or :has_many for "has_many :clients".
def macro
@macro
end
# Returns the hash of options used for the macro, so it would return { :class_name => "Money" } for
# "composed_of :balance, :class_name => 'Money'" or {} for "has_many :clients".
def options
@options
end
# Returns the class for the macro, so "composed_of :balance, :class_name => 'Money'" would return the Money class and
# "has_many :clients" would return the Client class.
def klass() end
def ==(other_aggregation)
name == other_aggregation.name && other_aggregation.options && active_record == other_aggregation.active_record
end
end
# Holds all the meta-data about an aggregation as it was specified in the Active Record class.
class AggregateReflection < MacroReflection #:nodoc:
def klass
Object.const_get(options[:class_name] || name_to_class_name(name.id2name))
end
private
def name_to_class_name(name)
name.capitalize.gsub(/_(.)/) { |s| $1.capitalize }
end
end
# Holds all the meta-data about an association as it was specified in the Active Record class.
class AssociationReflection < MacroReflection #:nodoc:
def klass
@klass ||= active_record.send(:compute_type, (name_to_class_name(name.id2name)))
end
def table_name
@table_name ||= klass.table_name
end
private
def name_to_class_name(name)
if name =~ /::/
name
else
unless class_name = options[:class_name]
class_name = name.to_s.camelize
class_name = class_name.singularize if [:has_many, :has_and_belongs_to_many].include?(macro)
end
active_record.send(:type_name_with_module, class_name)
end
end
end
end
end
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