Adding filter support to design docs

lib/couchrest/model/designs.rb

@@ -65,6 +65,17 @@ module CouchRest
           create_view_method(name)
         end
 
+        # Really simple design function that allows a filter
+        # to be added. Filters are simple functions used when listening
+        # to the _changes feed.
+        #
+        # No methods are created here, the design is simply updated.
+        # See the CouchDB API for more information on how to use this.
+        def filter(name, function)
+          filters = (self.model.design_doc['filters'] ||= {})
+          filters[name.to_s] = function
+        end
+
         def create_view_method(name)
           model.class_eval <<-EOS, __FILE__, __LINE__ + 1
             def self.#{name}(opts = {})

spec/couchrest/designs_spec.rb

@@ -87,6 +87,20 @@ describe "Design" do
 
     end
 
+    describe "#filter" do
+
+      before :each do
+        @object = @klass.new(DesignModel)
+      end
+
+      it "should add the provided function to the design doc" do
+        @object.filter(:important, "function(doc, req) { return doc.priority == 'high'; }")
+        DesignModel.design_doc['filters'].should_not be_empty
+        DesignModel.design_doc['filters']['important'].should_not be_blank
+      end
+
+    end
+
     describe "#create_view_method" do
       before :each do
         @object = @klass.new(DesignModel)