pokus

controllers.application\.js

import Controller from '@ember/controller';
import { action } from '@ember/object';
import {inject as service} from "@ember/service";

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
@service() store;

@action
act(){
   this.store.createRecord('my-model', {
     a: 'x',
     c: {
       b: 'y'
     }
   })
}

@action
act2(){
  console.log(this.store.peekAll('my-model'));
}
}

models.my-model2\.js

import Model from 'ember-data/model';

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


export default class extends Model {
  @attr('string') b;
}

models.my-model\.js

import Model from 'ember-data/model';

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


export default class extends Model {
  @attr('string') a;
  @belongsTo('my-model2') c;
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
<button {{action 'act'}}>act</button>
<button {{action 'act2'}}>act2</button>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}