Deprecation Guide for Initializer Arity

In prior versions of Ember initializers have taken two arguments (generally labeled as container and application). Starting with Ember 2.1 providing two arguments to an initializer will trigger a deprecation.

The following initializer for Ember 2.0 will trigger a deprecation:

export function initialize(container, application) {
  application.inject('route', 'service:session');
}

export default {
  name: 'inject-session',
  initialize: initialize
}

To clear the deprecation, remove the first argument (container in the above example):

export function initialize(application) {
  application.inject('route', 'service:session');
}

export default {
  name: 'inject-session',
  initialize: initialize
}

In some cases an addon might need to support both versions of Ember with the same initializer, one way to do this without triggering a deprecation would be the following (using the same example as above):

export function initialize() {
  let application = arguments[1] || arguments[0];
  application.inject('route', 'service:session');
}

export default {
  name: 'inject-session',
  initialize: initialize
}