class syntax + decorators

Tony Ward (@YnotDraw)

Ember's Learning Curve

Survey results always comment on the learning curve

2017 Results

2018 Results

Needs "Simplification of the mental model for Ember."
"If Ember were easier to learn..."

These are valid comments!

What can Ember do to improve?

(class syntax + decorators)

EmberConf 2018

JavaScript Support

  • TC39 introduced class syntax with ES6
  • Decorators are needed for things like computed properties and observers




How do we get there?

Medium article from Nov 2017 on class syntax + decorators in Ember

ES classes are already supported (RFC)


There's an Ember addon for that...

ember install ember-decorators

What is a decorator?

  • Python, Java, and other languages have them
  • "A function that takes another function and extends the behavior of the latter function without explicitly modifying it."


@concat("firstName", "lastName", " ") fullName;

function concat(...args) {
  let sep = args.pop(); // " "

  return function(target, key, descriptor) {
    descriptor.initializer = function() {
      return => this[arg]).join(sep);

ember-decorators goal

Its goal is to provide a set of decorators which can be used to write classes with every standard feature that is available in the standard Ember object-model, along with the transforms and build system required to polyfill and ship them today!

Demo App

Example Model

Example Route

Example Controller

Example Component

Component Arguments Addon

  • Help determine component arguments versus component state properties and their default values
  • Validate the argument type (string, number, action, closure action, etc.)
Positional Params are so much nicer - just use a `static` field
// before
const FooComponent = Component.extend({});

  positionalParams: ['bar', 'baz']

// after
class FooComponent extends Component {
  static positionalParams = ['bar', 'baz'];
Like code mods to convert everything for you? (issue)

A few things to be aware of:

Ember Inspector no longer works for models, but they're aware of it

Increased file size (for now)

"Running the decorator code through gzip and uglification results in a final file size of 293 bytes, so about 0.25 kbs per file that includes decorators."

No ember-cli support yet, still uses old blueprint (issue)


No longer relies on the Ember object model, instead uses native JS (lower barrier to entry for new devs)

Hopefully helps survey results with learning curve!

Declarative, clean syntax. Easier to read and reason about.

Can migrate code over incrementally - no need to convert all at once

(code mod will help here)

Really great documentation for the addon

Seriously, go check out the docs