Simplify Preloader#grouped_records code.

The new method relies on AR::Associations::Association knowing about both reflection and a model class.

AR::Base#association now raises a descriptive error when trying to access non-existent associations. Previously it would blow up with a confusing NoMethodError: undefined method `association_class' for nil:NilClass.

2 files changed, 13 insertions, 21 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 860e76fa18..4abe2ad0a0 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -4,6 +4,12 @@ require 'active_support/core_ext/module/remove_method'
 require 'active_record/errors'
 
 module ActiveRecord
+  class AssociationNotFoundError < ConfigurationError #:nodoc:
+    def initialize(record, association_name)
+      super("Association named '#{association_name}' was not found on #{record.class.name}; perhaps you misspelled it?")
+    end
+  end
+
   class InverseOfAssociationNotFoundError < ActiveRecordError #:nodoc:
     def initialize(reflection, associated_class = nil)
       super("Could not find the inverse association for #{reflection.name} (#{reflection.options[:inverse_of].inspect} in #{associated_class.nil? ? reflection.class_name : associated_class.name})")
@@ -145,7 +151,7 @@ module ActiveRecord
       association = association_instance_get(name)
 
       if association.nil?
-        reflection  = self.class.reflect_on_association(name)
+        raise AssociationNotFoundError.new(self, name) unless reflection = self.class.reflect_on_association(name)
         association = reflection.association_class.new(self, reflection)
         association_instance_set(name, association)
       end
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index e6485b2b0c..31ddf4e0fc 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -140,27 +140,13 @@ module ActiveRecord
       end
 
       def grouped_records(association, records)
-        reflection_records = records_by_reflection(association, records)
-
-        reflection_records.each_with_object({}) do |(reflection, r_records),h|
-          h[reflection] = r_records.group_by { |record|
-            record.association(association).klass
-          }
-        end
-      end
-
-      def records_by_reflection(association, records)
-        records.group_by do |record|
-          reflection = record.class.reflect_on_association(association)
-
-          reflection || raise_config_error(record, association)
+        h = {}
+        records.each do |record|
+          assoc = record.association(association)
+          klasses = h[assoc.reflection] ||= {}
+          (klasses[assoc.klass] ||= []) << record
         end
-      end
-
-      def raise_config_error(record, association)
-        raise ActiveRecord::ConfigurationError,
-              "Association named '#{association}' was not found on #{record.class.name}; " \
-              "perhaps you misspelled it?"
+        h
       end
 
       class AlreadyLoaded