New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  items: [],
  itemToAdd: null,
  
  submittedItems: null,
  
  actions: {
    add() {
      this.get('items').push(this.get('itemToAdd'));
      this.set('itemToAdd', null);
    },
    
    save() {
      this.set('submittedItems', this.get('items'));
      this.set('items', []);
      this.set('isSubmitted', true);
    },
    
    cancel() {
      this.set('items', []);
    }
  }
});

templates.application.hbs

<form {{action "save" on="submit"}}>
	<ul>
    {{#each items as |item|}}
    	<li>{{item}}</li>
    {{/each}}
  </ul>
  <div>
  	{{input value=itemToAdd}}
  	<button onclick={{action "add"}}>Add</button>
  </div>
  <button type="submit">Save</button>
  <button onclick={{action "cancel"}}>Cancel</button>
</form>

{{#if isSubmitted}}
	<h1>Success!</h1>
  <p>Your items are:</p>
  <ul>
  	{{#each submittedItems as |item|}}
    	<li>{{item}}</li>
    {{/each}}
  </ul>
{{/if}}

twiddle.json

{
  "version": "0.13.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.16.3"
  }
}