Map string keys to symbol keys

lib/mobility/attributes.rb

@@ -242,9 +242,13 @@ def get_class_from_key(parent_class, key)
     end
 
     module InstanceMethods
+      # Return a new backend for an attribute name.
+      # @return [Hash] Hash of attribute names and backend instances
       def mobility_backends
         @mobility_backends ||= Hash.new do |hash, name|
-          hash[name] = self.class.mobility_backend_class(name).new(self, name.to_s)
+          hash[name] = String === name ?
+            hash[name.to_sym] :
+            self.class.mobility_backend_class(name).new(self, name.to_s)
         end
       end
 

spec/mobility/attributes_spec.rb

@@ -155,6 +155,17 @@
           end
         end
 
+        it "maps string keys to symbol key values" do
+          mod = described_class.new("title", backend: :null)
+          Article.include mod
+
+          article = Article.new
+          expect(article.mobility_backends[:title]).to be_a(Mobility::Backends::Null)
+          expect(article.mobility_backends["title"]).to be_a(Mobility::Backends::Null)
+
+          expect(article.mobility_backends[:title]).to eq(article.mobility_backends["title"])
+        end
+
         it "resets when model is duplicated" do
           mod = described_class.new("title", backend: :null)
           Article.include mod