Question

I understand each and collection helper methods are two possible ways to iterate over a list of items in my handlebars templates. I am looking for some practical advice about when to use each or collection and what are the differences between the two methods.

Answer 1

Each:

App.myArray = [1,2,3]

{{#each value in App.myArray}}
  <p>{{value}}</p>
{{/each}}

corresponding HTML

<p>1</p>
<p>2</p>
<p>3</p>

Collection:

{{#collection contentBinding="App.myArray"}}
  <p>{{view.content}}</p>
{{/collection}}

corresponding HTML

<div class="ember-view">
  <p>1</p>
</div>
<div class="ember-view">
  <p>2</p>
</div>
<div class="ember-view">
  <p>3</p>
</div>

As you can see both deal with arrays. In a nutshell each is used to display an array of elements while collection is used to display an array of views

The main difference comes in practical use is when you want to interact with elements. If you just want to display a list of array use each helper.

But if you want to interact with each of the element in the array while maintaining context of the clicked element you collections

Let me explain with an example

App.CollectionView = Ember.CollectionView.extend({
  //Here the content belongs to collection view
  content: [1,2,3],
  itemViewClass: Ember.View.extend({
    /*This itemViewClass is like a template which is used by 
    all the elements in the content array of collection view*/
    click: function(){
      //Now this itemViewClass has a content property which is the single element in the collections content
      /* As you see the content of collection view has 3 elements => 3 templates 
         1 single template = Ember.View.extend with it's own content property
         first template has content set to 1
         second template has content set to 2 and so on...
      */
      alert("you clicked"+this.get('content');
    }
  })
})

I think this clears your doubt…