New Twiddle

controllers.application\.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  store: Ember.inject.service(),
  
  get firstThing() {
    return this.model.hasMany('things').value().firstObject;
  },
  
 	actions: {
  
  
  	updateUser: function() {
  		this.store.push({ 
      data: {
    		type: 'user',
      	id: 1,
        relationships: {
          things: {data:[{
            type: 'thing',
            id: 2
          }]}
        }
      },
      included: [{
        type: 'thing',
        id: 2
      }]
    	})
    }
	}
});

models.thing\.js

import Model from 'ember-data/model';
/*
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';
*/

export default Model.extend({
});

models.user\.js

import Model from 'ember-data/model';

import { hasMany } from 'ember-data/relationships';

export default Model.extend({
  things: hasMany('thing')
});

routes.application\.js

import Ember from 'ember';

export default Ember.Route.extend({
  
  model() {
    return this.store.push({ 
      data: {
    		type: 'user',
      	id: '1',
        relationships: {
          things: {data: [{
            type: 'thing',
            id: '1'
          }]}
        }
      },
      included: [{
         type: 'thing',
         id: '1'
      }]
    })
  }
});

templates.application\.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{model.id}}

{{this.firstThing.id}}

<button {{action 'updateUser'}}>Click</button>
<br>
<br>

twiddle\.json

{
  "version": "0.16.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.14.3",
    "ember-template-compiler": "3.14.3",
    "ember-testing": "3.14.3"
  },
  "addons": {
    "ember-data": "3.14.1"
  }
}