Remove builder instances

All the job can be done at class level so we can avoid some object
allocation

activerecord/lib/active_record/associations/builder/association.rb

@@ -18,18 +18,15 @@ class << self
 
     VALID_OPTIONS = [:class_name, :class, :foreign_key, :validate]
 
-    attr_reader :name, :scope, :options
-
     def self.build(model, name, scope, options, &block)
       extension = define_extensions model, name, &block
-      builder = create_builder model, name, scope, options, extension
-      reflection = builder.build(model)
+      reflection = create_reflection model, name, scope, options, extension
       define_accessors model, reflection
       define_callbacks model, reflection
       reflection
     end
 
-    def self.create_builder(model, name, scope, options, extension = nil)
+    def self.create_reflection(model, name, scope, options, extension = nil)
       raise ArgumentError, "association names must be a Symbol" unless name.kind_of?(Symbol)
 
       if scope.is_a?(Hash)
@@ -37,16 +34,11 @@ def self.create_builder(model, name, scope, options, extension = nil)
         scope   = nil
       end
 
-      new(name, scope, options, extension)
-    end
-
-    def initialize(name, scope, options, extension)
-      @name    = name
-      @options = options
+      validate_options(options)
 
-      self.class.validate_options(options)
+      scope = build_scope(scope, extension)
 
-      @scope = self.class.build_scope(scope, extension)
+      ActiveRecord::Reflection.create(macro, name, scope, options, model)
     end
 
     def self.build_scope(scope, extension)
@@ -67,10 +59,6 @@ def self.wrap_scope(scope, extension)
       scope
     end
 
-    def build(model)
-      ActiveRecord::Reflection.create(self.class.macro, name, scope, options, model)
-    end
-
     def self.macro
       raise NotImplementedError
     end

activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb

@@ -84,11 +84,11 @@ def middle_reflection(join_model)
       middle_name = [lhs_model.name.downcase.pluralize,
                      association_name].join('_').gsub(/::/, '_').to_sym
       middle_options = middle_options join_model
-      hm_builder = HasMany.create_builder(lhs_model,
-                                          middle_name,
-                                          nil,
-                                          middle_options)
-      hm_builder.build lhs_model
+
+      HasMany.create_reflection(lhs_model,
+                                middle_name,
+                                nil,
+                                middle_options)
     end
 
     private