Ember Dynamic aliases

gistfile1.js

import Ember from 'ember';

export default Ember.Object.extend({
    model: null,
    subpath: null,
    
    dynamicModelProperty: Ember.computed('model', 'subpath', function() {
        let subpath = this.get('subpath');

        if ( subpath ) {
            let DynamicClass = Ember.Object.extend({
                value: Ember.computed.alias(`model.${subpath}`)
            });

            return DynamicClass.create({model: this.get('model')});
        } else {
            return Ember.Object.create({});
        }
    }),

    value: Ember.computed.alias('dynamicModelProperty.value'),
});

AMAZING. Thank you! I killed the better part of a day trying to figure out a solution for this.

There is a probably simpler way, just replacing the computed alias whenever the subpath changes:

export default Ember.Component.extend({
  subpathObserver: Ember.observer('subpath', function(){
    this.value = Ember.computed.alias(`model.${this.get('subpath')}`)
    this.notifyPropertyChange('value');
  }).on('init')
});

@rewritten Your suggestion uses observers which (by nature) rely on side-effects. This can make code harder to reason about then simplifying the syntax. It also means that the computed property in question (value) is no longer lazy evaluated and you loos the performance benefits of the Ember run loop.

In general observers are an anti pattern. @schickm's original use of a computed proxy object may seem a bit more verbose but it doesn't suffer the negative impact that an observer would introduce.

DockYard has a nice post about observers: https://dockyard.com/blog/2015/11/16/best-practices-functional-programming-and-the-observer-effect