Bind Ember.Map to a Ember.TextField value - ember.js

Question

How can I bind an Ember Map value to a TextField value. Let's say I have this configuration:
App.AppsController = Em.Controller.extend({
selections: null
});
App.AppsRoute = Ember.Route.extend({
setupControllers: function(controller, model) {
controller.set('selections', Ember.Map.create());
}
});
And in my template:
{{view Ember.TextField valueBinding="bindingToMap"}}
I have tried to valueBinding="controller.selections.somekey" where somekey is a key from my map. However, the value is never bound. Note that initially the map is empty. Can this be the root of the problem?
EDIT:
I have also tried to use the binding with an integer value in the controller and it works. So the problem comes when I bind a more complex data structure such as a Map. I couldn't find anything in the docs explaining how to bind a map.

Answer 1

Caveat: I'm pretty new to Ember myself.
Looking at the implementation of Ember.Map, I don't think you can currently (in 1.0.0-pre2) do this. Ember.Map implements create, get, and set, but is not a normal Ember object. So among other things, "properties" in a map aren't really properties, and there's no observables support. The handlebars implementation relies heavily on observable support, so I think what you're doing won't work.
Someone correct me if I'm wrong, but this is what I'm looking at in the 1.0.0-pre2 code:
var Map = Ember.Map = function() {
this.keys = Ember.OrderedSet.create();
this.values = {};
};
/**
#method create
#static
*/
Map.create = function() {
return new Map();
};
Map.prototype = {
/**
Retrieve the value associated with a given key.
#method get
#param {anything} key
#return {anything} the value associated with the key, or undefined
*/
get: function(key) {
var values = this.values,
guid = guidFor(key);
return values[guid];
},
...
Point being, it implements its own get (and create) rather than extending Ember.Object...so no observable support. Though I might have missed it if it reopen's later or something.
EDIT:
Also, not really what you asked, but if you're building an interface that relies on the existence of some key, you should really probably be defining your own model class that has these keys as properties. You can still set them to null if they're "not set". If you also need the ability to set arbitrary keys, make one of your properties an Ember.Map and call it otherProperties or something, and put them in there. But if your view depends on a known key, it should be a defined property.