Add .count to extended documents to return how many there are.

Adds a reduce function to the default view so that an extra view doesn't have to be maintained just for the counting.

lib/couchrest/mixins/design_doc.rb

@@ -35,8 +35,11 @@ module CouchRest
               'all' => {
                 'map' => "function(doc) {
                   if (doc['couchrest-type'] == '#{self.to_s}') {
-                    emit(null,null);
+                    emit(null,1);
                   }
+                }",
+                'reduce' => "function(keys, values) {
+                  return sum(values);
                 }"
               }
             }

lib/couchrest/mixins/document_queries.rb

@@ -12,9 +12,18 @@ module CouchRest
         # name of the current class. Take the standard set of
         # CouchRest::Database#view options.
         def all(opts = {}, &block)
-          view(:all, opts, &block)
+          view(:all, {:reduce => false}.merge(opts), &block)
         end
-
+        
+        # Returns the number of documents that have the "couchrest-type" field
+        # equal to the name of the current class. Takes the standard set of 
+        # CouchRest::Database#view options
+        def count(opts = {}, &block)
+          result = all({:reduce => true}.merge(opts), &block)['rows']
+          return 0 if result.empty?
+          result.first['value']
+        end
+        
         # Load the first document that have the "couchrest-type" field equal to
         # the name of the current class.
         #

spec/couchrest/more/extended_doc_spec.rb

@@ -241,7 +241,25 @@ describe "ExtendedDocument" do
       rs.length.should == 4
     end
   end
-
+  
+  describe "counting all instances of a model" do
+    before(:each) do
+      @db = reset_test_db!
+    end
+    
+    it ".count should return 0 if there are no docuemtns" do
+      WithTemplateAndUniqueID.count.should == 0
+    end
+    
+    it ".count should return the number of documents" do
+      WithTemplateAndUniqueID.new('important-field' => '1').save
+      WithTemplateAndUniqueID.new('important-field' => '2').save
+      WithTemplateAndUniqueID.new('important-field' => '3').save
+      
+      WithTemplateAndUniqueID.count.should == 3
+    end
+  end
+  
   describe "finding the first instance of a model" do
     before(:each) do      
       @db = reset_test_db!