Add option to omit creating an instance reader method on class_attribute

activesupport/lib/active_support/core_ext/class/attribute.rb

@@ -56,11 +56,22 @@ class Class
   #   object.setting          # => false
   #   Base.setting            # => true
   #
+  # To opt out of the instance reader method, pass :instance_reader => false.
+  #
+  #   object.setting          # => NoMethodError
+  #   object.setting?         # => NoMethodError
+  #
   # To opt out of the instance writer method, pass :instance_writer => false.
   #
   #   object.setting = false  # => NoMethodError
   def class_attribute(*attrs)
-    instance_writer = !attrs.last.is_a?(Hash) || attrs.pop[:instance_writer]
+    instance_reader = true
+    instance_writer = true
+    if attrs.last.is_a?(Hash)
+      instance_accessors = attrs.pop
+      instance_reader = instance_accessors[:instance_reader]
+      instance_writer = instance_accessors[:instance_writer]
+    end
 
     attrs.each do |name|
       class_eval <<-RUBY, __FILE__, __LINE__ + 1
@@ -84,13 +95,15 @@ def #{name}
           val
         end
 
-        remove_possible_method :#{name}
-        def #{name}
-          defined?(@#{name}) ? @#{name} : self.class.#{name}
-        end
+        if instance_reader
+          remove_possible_method :#{name}
+          def #{name}
+            defined?(@#{name}) ? @#{name} : self.class.#{name}
+          end
 
-        def #{name}?
-          !!#{name}
+          def #{name}?
+            !!#{name}
+          end
         end
       RUBY
 

activesupport/test/core_ext/class/attribute_test.rb

@@ -60,6 +60,12 @@ def setup
     assert_raise(NoMethodError) { object.setting = 'boom' }
   end
 
+  test 'disabling instance reader' do
+    object = Class.new { class_attribute :setting, :instance_reader => false }.new
+    assert_raise(NoMethodError) { object.setting }
+    assert_raise(NoMethodError) { object.setting? }
+  end
+
   test 'works well with singleton classes' do
     object = @klass.new
     object.singleton_class.setting = 'foo'