1 files changed, 31 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/module/attr_internal.rb b/activesupport/lib/active_support/core_ext/module/attr_internal.rb
new file mode 100644
index 0000000000..c793da7159
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/module/attr_internal.rb
@@ -0,0 +1,31 @@
+class Module
+  # Declare an attribute reader backed by an internally-named instance variable.
+  def attr_internal_reader(*attrs)
+    attrs.each do |attr|
+      module_eval "def #{attr}() #{attr_internal_ivar_name(attr)} end"
+    end
+  end
+
+  # Declare an attribute writer backed by an internally-named instance variable.
+  def attr_internal_writer(*attrs)
+    attrs.each do |attr|
+      module_eval "def #{attr}=(v) #{attr_internal_ivar_name(attr)} = v end"
+    end
+  end
+
+  # Declare attributes backed by 'internal' instance variables names.
+  def attr_internal_accessor(*attrs)
+    attr_internal_reader *attrs
+    attr_internal_writer *attrs
+  end
+
+  alias_method :attr_internal, :attr_internal_accessor
+
+  private
+    mattr_accessor :attr_internal_naming_format
+    self.attr_internal_naming_format = '@_%s'
+
+    def attr_internal_ivar_name(attr)
+      attr_internal_naming_format % attr
+    end
+end