Lookup superclasses when determining #admin_for instance

app/helpers/trestle/url_helper.rb

@@ -49,7 +49,17 @@ def admin_url_for(instance, options={})
     end
 
     def admin_for(instance)
-      Trestle.admins[instance.class.name.underscore.pluralize]
+      klass = instance.class
+
+      while klass
+        admin = Trestle.admins[klass.name.underscore.pluralize]
+        return admin if admin
+
+        klass = klass.superclass
+      end
+
+      # No admin found
+      nil
     end
   end
 end

spec/trestle/helpers/url_helper_spec.rb

@@ -120,10 +120,22 @@
   end
 
   describe "#admin_for" do
-    let(:instance) { double(class: double(name: "MyClass")) }
+    before(:each) do
+      allow(Trestle).to receive(:admins).and_return({ "my_classes" => admin})
+    end
 
     it "returns the admin associated with an object's class type" do
-      expect(Trestle).to receive(:admins).and_return({ "my_classes" => admin})
+      klass = double(name: "MyClass", superclass: nil)
+      instance = double(class: klass)
+
+      expect(admin_for(instance)).to eq(admin)
+    end
+
+    it "tries the object class's ancestors" do
+      parent = double(name: "MyClass", superclass: nil)
+      klass = double(name: "Subclass", superclass: parent)
+      instance = double(class: klass)
+
       expect(admin_for(instance)).to eq(admin)
     end
   end