Teach me how to design a nested computed property in ember.js - ember.js

Question

I have a handful of computed properties defined on a component. I'd like to refactor these computed properties to live within a messages object on the component. When I make a call to get one of the computed properties elsewhere, I'm returned an instance of Ember's ComputedProperty object, rather then the translation string I expected. Looking at the documentation, Ember.get should invoke the computed property and return the object itself, the property value or null.
What am I missing? How would I go about structuring these nested computed properties so that I can access them using the get/set interface elsewhere in the component?
App.ValidatedDateComponent = Ember.Component.extend({
format: null,
label: null,
messages: {
invalidDateMsg: (function() {
return I18n.t('%{date} must be a valid date. %{format}', {
date: this.get('label'),
format: this.get('format')
});
}).property('label', 'format')
},
validate: function(value, status) {
if (!moment(value).isValid()) {
return status(false, Ember.get(this.messages, 'invalidDateMsg'));
} else {
return this._super(value, status);
}
}
});

Answer 1

Ember only supports defining computed properties while extending Ember.Object class, the exception to the rule is while defining a Ember.Mixin.
Defining the top level of the nest
var nest = Ember.Object.extend({
foo: function() {
return "something";
}.property()
});
Creating an instance of it
App.IndexController = Em.ArrayController.extend({
messages: nest.create()
});
Template
{{messages.foo}}
http://emberjs.jsbin.com/UhUvOvU/1/edit
So in your case you could, if you really wanted to, do:
messages: Em.Object.extend({
invalidDateMsg: function() {
return I18n.t('%{date} must be a valid date. %{format}', {
date: this.get('label'),
format: this.get('format')
});
}.property('label', 'format')
}).create(),