New Twiddle

components.message-ui.js

import Ember from 'ember';

const {computed} = Ember;

export default Ember.Component.extend({
  previousMessage: computed('index', function(){
  	return this.get('messages').objectAt(this.get('index') - 1)
  }),
  isDoublePost: computed('previousMessage.content', 'model.content', function(){
    console.log(this.get('messages'));
  	return this.get('previousMessage.content') === this.get('model.content')
  })
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  newMessage: '',
  messages: [
    {
    	id: 1,
      content: 'First'
    },
    {
    	id: 2,
      content: 'Second'
    },
    {
    	id: 3,
      content: 'Third'
    },
    {
    	id: 4,
      content: 'Third'
    }
  ],
  actions: {
  	add(){
    	this.get('messages').pushObject({
      	content: this.get('newMessage')
      });
      
      this.set('newMessage', null);
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{#each messages as |message index|}}
	{{message-ui model=message index=index messages=messages}}
{{/each}}

{{input value=newMessage}}
<button {{action "add"}}>Add</button> 

templates.components.message-ui.hbs

{{#unless isDoublePost}}
{{model.content}}
{{/unless}}

twiddle.json

{
  "version": "0.8.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.5.1",
    "ember-data": "2.5.2",
    "ember-template-compiler": "2.5.1"
  }
}