Using typescript classes for services in angular 1.4.7

Question

I'm trying to implement services as classes as per this Ng Conf video Angular 1.3 meets Angular 2.0 - Michał Gołębiowski :

https://youtu.be/pai1ZdFI2dg?t=4m25s

I keep getting this error:

TypeError: Cannot read property 'prototype' of undefined

Code below:

var angular = window['angular'];
angular
    .module('myApp', [])
    .service('myService', [MyService])
    .directive('test', function (myService) {
        return {
            restricts: 'E',
            template: 'Directive output: {{ctrl.message}}',
            controllerAs: 'ctrl',
            controller: function () {
                this.message = myService.message;
            }   
        }
    });

/*
// Works
function MyService () {
  return {
      message: "service test"
    }
}
*/

// Does not work
class MyService {
  public message:string;
  constructor () {
    this.message = "service test by class";
  }
}

http://codepen.io/AshCoolman/pen/PPLONm?editors=001

EDIT: Solution

Simple wrapping the class works, and that will do for now:

.service('myService', function () {return new MyService()})

Actually it seems quite straight forward now I think of it. The example video is using es6 perhaps with Babel, while I'm using Typescript. At a guess , Typescript/Tracuer is probably doing things differently. I will look into this later tonight and post a full explanation.

EDIT: Explanation

Martin Vseticka beat me to it, see below.

Answer 1

The line

.service('myService', [MyService])

should be

.service('myService', MyService)

Edit: The solution is more simple I guess :-) The approach with

function MyService () {
  return {
      message: "service test"
    }
}

works because functions are hoisted in JavaScript.

However, the following TypeScript code

class MyService {
  public message:string;
  constructor () {
    this.message = "service test by class";
  }
}

is transpiled to:

var MyService = (function () {
    function MyService() {
        this.message = "service test by class";
    }
    return MyService;
})();

which means that .service('myService', MyService) cannot work because MyService is not defined (ie MyService = undefined ) at that point!