module ActiveRecord module Associations # This is the root class of all association proxies: # # AssociationProxy # BelongsToAssociation # HasOneAssociation # BelongsToPolymorphicAssociation # AssociationCollection # HasAndBelongsToManyAssociation # HasManyAssociation # HasManyThroughAssociation # HasOneThroughAssociation # # Association proxies in Active Record are middlemen between the object that # holds the association, known as the @owner, and the actual associated # object, known as the @target. The kind of association any proxy is # about is available in @reflection. That's an instance of the class # ActiveRecord::Reflection::AssociationReflection. # # For example, given # # class Blog < ActiveRecord::Base # has_many :posts # end # # blog = Blog.find(:first) # # the association proxy in blog.posts has the object in +blog+ as # @owner, the collection of its posts as @target, and # the @reflection object represents a :has_many macro. # # This class has most of the basic instance methods removed, and delegates # unknown methods to @target via method_missing. As a # corner case, it even removes the +class+ method and that's why you get # # blog.posts.class # => Array # # though the object behind blog.posts is not an Array, but an # ActiveRecord::Associations::HasManyAssociation. # # The @target object is not loaded until needed. For example, # # blog.posts.count # # is computed directly through SQL and does not trigger by itself the # instantiation of the actual post records. class AssociationProxy #:nodoc: alias_method :proxy_respond_to?, :respond_to? alias_method :proxy_extend, :extend delegate :to_param, :to => :proxy_target instance_methods.each { |m| undef_method m unless m =~ /(^__|^nil\?$|^send$|proxy_|^object_id$)/ } def initialize(owner, reflection) @owner, @reflection = owner, reflection Array(reflection.options[:extend]).each { |ext| proxy_extend(ext) } reset end def proxy_owner @owner end def proxy_reflection @reflection end def proxy_target @target end def respond_to?(*args) proxy_respond_to?(*args) || (load_target && @target.respond_to?(*args)) end # Explicitly proxy === because the instance method removal above # doesn't catch it. def ===(other) load_target other === @target end def aliased_table_name @reflection.klass.table_name end def conditions @conditions ||= interpolate_sql(sanitize_sql(@reflection.options[:conditions])) if @reflection.options[:conditions] end alias :sql_conditions :conditions def reset @loaded = false @target = nil end def reload reset load_target self unless @target.nil? end def loaded? @loaded end def loaded @loaded = true end def target @target end def target=(target) @target = target loaded end def inspect load_target @target.inspect end protected def dependent? @reflection.options[:dependent] end def quoted_record_ids(records) records.map { |record| record.quoted_id }.join(',') end def interpolate_sql(sql, record = nil) @owner.send(:interpolate_sql, sql, record) end def sanitize_sql(sql) @reflection.klass.send(:sanitize_sql, sql) end def set_belongs_to_association_for(record) if @reflection.options[:as] record["#{@reflection.options[:as]}_id"] = @owner.id unless @owner.new_record? record["#{@reflection.options[:as]}_type"] = @owner.class.base_class.name.to_s else record[@reflection.primary_key_name] = @owner.id unless @owner.new_record? end end def merge_options_from_reflection!(options) options.reverse_merge!( :group => @reflection.options[:group], :limit => @reflection.options[:limit], :offset => @reflection.options[:offset], :joins => @reflection.options[:joins], :include => @reflection.options[:include], :select => @reflection.options[:select], :readonly => @reflection.options[:readonly] ) end def with_scope(*args, &block) @reflection.klass.send :with_scope, *args, &block end private def method_missing(method, *args) if load_target if block_given? @target.send(method, *args) { |*block_args| yield(*block_args) } else @target.send(method, *args) end end 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 return nil unless defined?(@loaded) if !loaded? and (!@owner.new_record? || foreign_key_present) @target = find_target end @loaded = true @target rescue ActiveRecord::RecordNotFound reset end # Can be overwritten by associations that might have the foreign key available for an association without # having the object itself (and still being a new record). Currently, only belongs_to presents this scenario. def foreign_key_present false end def raise_on_type_mismatch(record) unless record.is_a?(@reflection.klass) message = "#{@reflection.class_name}(##{@reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})" raise ActiveRecord::AssociationTypeMismatch, message end end # Array#flatten has problems with recursive arrays. Going one level deeper solves the majority of the problems. def flatten_deeper(array) array.collect { |element| element.respond_to?(:flatten) ? element.flatten : element }.flatten end end end end