205 lines
8.2 KiB
Ruby
205 lines
8.2 KiB
Ruby
module ActiveRecord
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module Reflection # :nodoc:
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def self.included(base)
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base.extend(ClassMethods)
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end
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# Reflection allows you to interrogate Active Record classes and objects about their associations and aggregations.
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# This information can, for example, be used in a form builder that took an Active Record object and created input
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# fields for all of the attributes depending on their type and displayed the associations to other objects.
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#
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# You can find the interface for the AggregateReflection and AssociationReflection classes in the abstract MacroReflection class.
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module ClassMethods
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def create_reflection(macro, name, options, active_record)
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case macro
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when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
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reflection = AssociationReflection.new(macro, name, options, active_record)
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when :composed_of
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reflection = AggregateReflection.new(macro, name, options, active_record)
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end
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write_inheritable_hash :reflections, name => reflection
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reflection
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end
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def reflections
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read_inheritable_attribute(:reflections) or write_inheritable_attribute(:reflections, {})
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end
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# Returns an array of AggregateReflection objects for all the aggregations in the class.
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def reflect_on_all_aggregations
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reflections.values.select { |reflection| reflection.is_a?(AggregateReflection) }
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end
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# Returns the AggregateReflection object for the named +aggregation+ (use the symbol). Example:
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# Account.reflect_on_aggregation(:balance) # returns the balance AggregateReflection
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def reflect_on_aggregation(aggregation)
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reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
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end
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# Returns an array of AssociationReflection objects for all the aggregations in the class. If you only want to reflect on a
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# certain association type, pass in the symbol (:has_many, :has_one, :belongs_to) for that as the first parameter. Example:
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# Account.reflect_on_all_associations # returns an array of all associations
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# Account.reflect_on_all_associations(:has_many) # returns an array of all has_many associations
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def reflect_on_all_associations(macro = nil)
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association_reflections = reflections.values.select { |reflection| reflection.is_a?(AssociationReflection) }
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macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
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end
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# Returns the AssociationReflection object for the named +aggregation+ (use the symbol). Example:
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# Account.reflect_on_association(:owner) # returns the owner AssociationReflection
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# Invoice.reflect_on_association(:line_items).macro # returns :has_many
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def reflect_on_association(association)
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reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
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end
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end
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# Abstract base class for AggregateReflection and AssociationReflection that describes the interface available for both of
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# those classes. Objects of AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods.
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class MacroReflection
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attr_reader :active_record
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def initialize(macro, name, options, active_record)
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@macro, @name, @options, @active_record = macro, name, options, active_record
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end
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# Returns the name of the macro, so it would return :balance for "composed_of :balance, :class_name => 'Money'" or
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# :clients for "has_many :clients".
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def name
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@name
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end
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# Returns the name of the macro, so it would return :composed_of for
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# "composed_of :balance, :class_name => 'Money'" or :has_many for "has_many :clients".
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def macro
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@macro
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end
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# Returns the hash of options used for the macro, so it would return { :class_name => "Money" } for
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# "composed_of :balance, :class_name => 'Money'" or {} for "has_many :clients".
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def options
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@options
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end
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# Returns the class for the macro, so "composed_of :balance, :class_name => 'Money'" would return the Money class and
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# "has_many :clients" would return the Client class.
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def klass() end
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def class_name
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@class_name ||= name_to_class_name(name.id2name)
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end
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def ==(other_aggregation)
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name == other_aggregation.name && other_aggregation.options && active_record == other_aggregation.active_record
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end
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end
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# Holds all the meta-data about an aggregation as it was specified in the Active Record class.
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class AggregateReflection < MacroReflection #:nodoc:
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def klass
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@klass ||= Object.const_get(options[:class_name] || class_name)
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end
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private
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def name_to_class_name(name)
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name.capitalize.gsub(/_(.)/) { |s| $1.capitalize }
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end
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end
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# Holds all the meta-data about an association as it was specified in the Active Record class.
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class AssociationReflection < MacroReflection #:nodoc:
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def klass
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@klass ||= active_record.send(:compute_type, class_name)
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end
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def table_name
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@table_name ||= klass.table_name
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end
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def primary_key_name
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return @primary_key_name if @primary_key_name
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case
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when macro == :belongs_to
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@primary_key_name = options[:foreign_key] || class_name.foreign_key
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when options[:as]
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@primary_key_name = options[:foreign_key] || "#{options[:as]}_id"
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else
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@primary_key_name = options[:foreign_key] || active_record.name.foreign_key
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end
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end
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def association_foreign_key
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@association_foreign_key ||= @options[:association_foreign_key] || class_name.foreign_key
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end
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def counter_cache_column
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if options[:counter_cache] == true
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"#{active_record.name.underscore.pluralize}_count"
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elsif options[:counter_cache]
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options[:counter_cache]
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end
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end
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def through_reflection
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@through_reflection ||= options[:through] ? active_record.reflect_on_association(options[:through]) : false
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end
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# Gets an array of possible :through source reflection names
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#
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# [singularized, pluralized]
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def source_reflection_names
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@source_reflection_names ||= (options[:source] ? [options[:source]] : [name.to_s.singularize, name]).collect { |n| n.to_sym }
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end
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# Gets the source of the through reflection. It checks both a singularized and pluralized form for :belongs_to or :has_many.
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# (The :tags association on Tagging below)
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#
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# class Post
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# has_many :tags, :through => :taggings
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# end
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#
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def source_reflection
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return nil unless through_reflection
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@source_reflection ||= source_reflection_names.collect { |name| through_reflection.klass.reflect_on_association(name) }.compact.first
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end
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def check_validity!
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if options[:through]
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if through_reflection.nil?
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raise HasManyThroughAssociationNotFoundError.new(self)
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end
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if source_reflection.nil?
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raise HasManyThroughSourceAssociationNotFoundError.new(self)
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end
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if source_reflection.options[:polymorphic]
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raise HasManyThroughAssociationPolymorphicError.new(class_name, self, source_reflection)
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end
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unless [:belongs_to, :has_many].include?(source_reflection.macro) && source_reflection.options[:through].nil?
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raise HasManyThroughSourceAssociationMacroError.new(self)
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end
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end
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end
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private
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def name_to_class_name(name)
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if name =~ /::/
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name
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else
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if options[:class_name]
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options[:class_name]
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elsif through_reflection # get the class_name of the belongs_to association of the through reflection
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source_reflection.class_name
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else
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class_name = name.to_s.camelize
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class_name = class_name.singularize if [ :has_many, :has_and_belongs_to_many ].include?(macro)
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class_name
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end
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end
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end
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end
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end
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end
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