Ember: default behaviour of `Route#model()`

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

helpers.stringify.js

import Ember from 'ember';

export function stringify(params) {
  return JSON.stringify(params[0]);
}

export default Ember.Helper.helper(stringify);

router.js

import Ember from 'ember';
import config from './config/environment';

const Router = Ember.Router.extend({
  location: 'none',
  rootURL: config.rootURL
});

Router.map(function() {
  this.route('parent', { path: 'parents/:parent_id' }, function() {
    this.route('child', { path: 'children/:child_id' });
  });
});

export default Router;

routes.parent.child.js

import Ember from 'ember';

export default Ember.Route.extend({
  store: Ember.inject.service(),
});

routes.parent.js

import Ember from 'ember';

export default Ember.Route.extend({
  store: Ember.inject.service(),
});

services.store.js

import Ember from 'ember';

export default Ember.Service.extend({
  find(modelName, id, options) {
    return {
      findArgs: {
        modelName,
        id,
        options
    	}
    };
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>

{{outlet}}

<p>{{link-to "To parent route" 'parent' 'provided-parent-id'}}</p>
<p>{{link-to "To child route" 'parent.child' 'provided-parent-id' 'provided-child-id'}}</p>

templates.parent.child.hbs

<h2>Child template</h2>
<p>Model:</p>
<pre>{{stringify model}}</pre>

templates.parent.hbs

<h2>Parent template</h2>
<p>Model:</p>
<pre>{{stringify model}}</pre>

{{outlet}}

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  }
}