testing on twiddle

controllers.application.js

import Controller from '@ember/controller';
import { reads } from '@ember/object/computed';

export default Controller.extend({
  children: reads('model'),
  actions: {
    clickChild(child) {
      child.parent.then(parent => {
        console.log(parent.name);
      });
    }
  }
});

mirage.config.js

export default function() {
  this.resource('message-thread');
  this.resource('message-message');
  this.resource('user');
}

mirage.factories.message-message.js

import { Factory } from 'ember-cli-mirage';

export default Factory.extend({
  name(i) { return `Message message-${i}`; }
});

mirage.factories.message-thread.js

import { Factory } from 'ember-cli-mirage';

export default Factory.extend({
  name(i) { return `Thread-${i}`; }
});

mirage.factories.user.js

import { Factory } from 'ember-cli-mirage';

export default Factory.extend({
  name(i) { return `User-${i}`; }
});

mirage.scenarios.default.js

export default function(server) {
  let messageThread = server.create('message-thread');
  let messageThread2 = server.create('message-thread');
  let user = server.create('user');

  server.createList('message-message', 10, { messageThread, user });
  server.createList('message-message', 10, { messageThread: messageThread2, user });
}

mirage.serializers.application.js

import { JSONAPISerializer } from 'ember-cli-mirage';

export default JSONAPISerializer.extend({
  alwaysIncludeLinkageData: true,
});

models.message-message.js

import DS from 'ember-data'
const {Model, attr, hasMany, belongsTo} = DS

export default DS.Model.extend({
  messageThread: belongsTo('message-thread', { async: true }),
  user: belongsTo("user", {async: true}),
  
  name: attr(),
});

models.message-thread.js

import DS from 'ember-data'
const {Model, attr, hasMany, belongsTo} = DS

export default DS.Model.extend({
  messageMessages: hasMany({ async: true }),

  name: attr(),
});

models.user.js

import DS from 'ember-data'
const {Model, attr, hasMany} = DS

export default Model.extend({
  name: attr(),
  messageMessages: hasMany(),
});

routes.application.js

import Route from '@ember/routing/route';

export default Route.extend({
  model() {
    return this.store.findAll('message-thread');
  }
});

templates.application.hbs

{{#each model as |thread|}}
	<h1>Thread {{thread.id}}</h1>
  {{#each thread.messageMessages as |message|}}
 		<p>
    	<strong>{{message.name}}</strong>
	    {{message.user.name}}
    </p>
  {{/each}}
{{/each}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "ENV": {
    "ember-cli-mirage": {
      "enabled": true
    }
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.9.0",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.11.0",
    "ember-cli-mirage": "0.4.6"
  }
}