Bug fix and improvement to handling of :relationships in to_json method

lib/dm-serializer/to_json.rb

@@ -39,7 +39,12 @@ def as_json(options = {})
       # TODO: This needs tests and also needs to be ported to #to_xml and
       # #to_yaml
       if options[:relationships]
-        options[:relationships].each do |relationship_name, opts|
+        # check for symbol or string argument, and splat-collect if we have one
+        rel = options[:relationships]
+        rel = *rel if (rel.kind_of?(Symbol) || rel.kind_of?(String))
+        rel.each do |relationship_name, opts|
+          # opts will be null from splat, or with nested :relationships
+          opts ||= {}
           if respond_to?(relationship_name)
             result[relationship_name] = __send__(relationship_name).to_json(opts.merge(:to_json => false))
           end

spec/public/to_json_spec.rb

@@ -69,6 +69,17 @@ def deserialize(result)
     expect { Cow.new.as_json(nil) }.to_not raise_error
   end
 
+  it "handles nil for :relationships => options" do
+    # This is to prevent :relationships having to be called as:
+    # cow.to_json(:relationships => {:baby_cows => {}})
+    expect { Cow.new.as_json(:relationships => [:baby_cows])}.to_not raise_error
+    end
+
+    it "handles string and symbol arguments for :relationships" do
+      expect { Cow.new.as_json(:relationships => :baby_cows)}.to_not raise_error
+      expect { Cow.new.as_json(:relationships => 'baby_cows')}.to_not raise_error  
+      end
+
   it "serializes Discriminator types as strings" do
     Motorcycle.new.as_json[:type].should == "Motorcycle"
   end