ObjectProxy DS.HasMany

adapters.application.js

import Adapter from "ember-data/adapters/json-api";

export default Adapter.extend();

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  actions: {
    newPage: function(wrappedBook){
      Ember.$.ajax('/change_stuff').then(
        () => {
          wrappedBook.get('content').reload();
        }
      );
    }
  },
});

initializers.pretender.js

export function json(status, body) {
  if (arguments.length === 1) {
    body = status;
    status = 200;
  }
  
  return [
    status,
    { "Content-Type": "application/json" },
    JSON.stringify(body)
  ];
};

export const server = new Pretender();

export function initialize() {
  server.handledRequest = function(verb, path, request) {
    console.log(`handled request to ${verb} ${path}`);
  }

  server.unhandledRequest = function(verb, path, request) {
    console.log(`undhandled request ${verb} ${path}`);
  }
};

export default {
  name: 'pretender',
  initialize
};

models.book.js

import Model from "ember-data/model";
import DS from "ember-data";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
  pages: DS.hasMany('page'),

  numPages: Ember.computed('pages.[]', function() {
    return this.hasMany('pages').ids().length;
  }),
});

models.page.js

import Model from "ember-data/model";
import DS from "ember-data";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
  book: DS.belongsTo('book'),
});

routes.application.js

import Ember from 'ember';
import { server, json } from '../initializers/pretender';

let i = 0;
let pagesData = [];

server.map(function() {
  this.get('change_stuff', function() {
    pagesData.push({ type: "pages", id: i++});
    return [
      200,
      {'content-type': 'application/javascript'},
      '',
    ];
  });
  
  this.get('/books/1', function() {
    return json({
      data: {
        type: 'book',
        id: 1,
        relationships: {
          pages: {
            links: {
              self: "/books/1/relationships/pages",
              related: "/books/1/pages"
            },
            data: pagesData
          }
        },
      },
    });
  });
});

const BookWrapper = Ember.ObjectProxy.extend({
  //numPages: Ember.computed('pages.[]', function() {
  //numPages: Ember.computed('content.pages.[]', function() {
  //  return this.get('content').hasMany('pages').ids().length;
  //}),
});

export default Ember.Route.extend({
  model: function() {
    return this.store.findRecord('book', 1).then(
      (book) => BookWrapper.create({ content: book })
    );
  },
});

serializers.application.js

import Serializer from "ember-data/serializers/json-api";

export default Serializer.extend();

templates.application.hbs

<div>numPages: {{model.numPages}}</div>
<button onClick={{action 'newPage' model}}>New</button>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0",
    "route-recognizer": "https://rawgit.com/tildeio/route-recognizer/56f5fcec6ae58d8e86b5dc77609809fb91198142/dist/route-recognizer.js",
    "FakeXMLHttpRequest": "https://rawgit.com/pretenderjs/FakeXMLHttpRequest/23c3a96b5b24f1bfe595867437e4f128a29c2840/fake_xml_http_request.js",
    "pretender": "https://rawgit.com/pretenderjs/pretender/c6de9afe18b1472aded2592f5a80ad9a26a0e262/pretender.js"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}