1 files changed, 17 insertions, 0 deletions
diff --git a/lib/arel/extensions/class.rb b/lib/arel/extensions/class.rb
new file mode 100644
index 0000000000..0e5b728c26
--- /dev/null
+++ b/lib/arel/extensions/class.rb
@@ -0,0 +1,17 @@
+class Class
+  def abstract(*methods)
+    methods.each do |method|
+      define_method method do
+        raise NotImplementedError
+      end
+    end
+  end
+  
+  def hash_on(delegatee)
+    define_method :eql? do |other|
+      self == other
+    end
+    
+    delegate :hash, :to => delegatee
+  end
+end
+\ No newline at end of file