Hard-fought Ember promise CP that actually resolves in template

promisemodel.hbs

{{model.allVariantsQty.value}}

promisemodel.js

allVariantsQty: Ember.computed('productVariants.@each.inventoryQuantity', function (){
  var result = this.get('productVariants').then(resolved => {
    var reducedQty = resolved.map( aVar => aVar.get('inventoryQuantity')).reduce((a,b) => a + b, 0);
    return Ember.RSVP.resolve({value:reducedQty});
  });
  return DS.PromiseObject.create({
    promise:result
  });
}),

This is the Holy Grail, for getting deep references on the model (or wherever) that play nice with templates. In this case, product.productVariant.aggregatedQuantity. Seems simple, but it's a real hassle, because templates aren't promise-aware & you're "supposed" to do this stuff on the route's model hook.

Further reading:

• https://emberigniter.com/guide-promises-computed-properties/
• http://stackoverflow.com/questions/30132283/model-promise-causing-template-to-use-content