Empty controller blocks view. Why? - ember.js

Question

I have been experimenting with using Ember with a JSON server but without without ember-data. My test app renders a directory of images from a small JSON structure (generated from a little Go server).
Can anyone explain to me why, if I uncomment the App.FileController in the code below, the corresponding File view fails to render?
window.App = Ember.Application.create();
App.Router.map(function() {
this.resource('files',function(){
this.resource('file',{path:':file_id'});
});
});
App.FilesRoute = Ember.Route.extend({
model: function() {
return App.File.findAll();
}
});
App.FileRoute = Ember.Route.extend({
setupController: function(controller, args) {
controller.set('model', App.File.find(args.id));
},
model: function(args) {
return App.File.find(args.file_id);
}
});
App.File = Ember.Object.extend({
urlPath: function(){
return "/pics/" + this.get('id');
}.property('id'),
});
If I uncomment this, things break:
// App.FileController = Ember.Controller.extend({
// });
(namely, the File sub-view no longer renders at all.)
App.File.reopenClass({
find: function(id){
file = App.File.create({'id':id});
return file;
},
findAll: function() {
return $.getJSON("http://localhost:8080/api/").then(
function(response) {
var files = [];
response.Files.forEach(function (filename) {
files.push(App.File.create({'id':filename}));
});
return files;
}
);
},
});
Also, is there something fundamental that I'm doing wrong here?

Answer 1

As noted by Finn MacCool and agmcleod I was trying to use the wrong type of controller. The correct lines should be:
App.FileController = Ember.ObjectController.extend({
});
Not that I need to explicitly set a FileController in this small example. However, should I go on to expand the code I will no doubt need one and will need to use the correct one.