each with index and modulo in ember and handlebar

Question

I'm creating a slide - so there's 3 images every one div like so

<div>
  <img />
  <img />
  <img />
</div>

</div>
  <img />
  <img />
  <img />
</div>

None of the code around the internet works flawlessly -

https://github.com/johanpoirier/resthub-backbone-stack/commit/8a318477d56c370d2a0af4da6eae9999c7bb29da

http://jaketrent.com/post/every-nth-item-in-handlebars-loop/

http://rockycode.com/blog/handlebars-loop-index/

http://www.arlocarreon.com/blog/javascript/handlebars-js-everyother-helper/

and yes including the answers here in stack overflow.

Can anyone provide some code that works perfectly at this current period (version of Ember/Handlebar)?

I have an array of models so i'd like to do something like

{{#each model}}
    {{if index % 3 == 0}}
    {{/if}}
{{/each}}

Answer 1

I have been finding that index or @index do not work from within the template, but you can access it from within a helper.

I've made an example here that demonstrates this:

http://jsbin.com/egoyay/1/edit

Edit: Adding code to answer, demonstrating {{else}} block

Handlebars helper (for non-Ember use):

Handlebars.registerHelper('ifIsNthItem', function(options) {
  var index = options.data.index + 1,
      nth = options.hash.nth;

  if (index % nth === 0) 
    return options.fn(this);
  else
    return options.inverse(this);
});

Usage:

<ol>
 {{#each model}}
   <li>
     {{#ifIsNthItem nth=3}}
        Index is a multiple of 3
     {{else}}
        Index is NOT a multiple of 3
     {{/ifIsNthItem}}
   </li>
 {{/each}}
</ol>

Answer 2

If you specify itemViewClass in each helper, then it will create a view for each item and set contentIndex property:

{{#each model itemViewClass="Ember.View"}}
    {{view.contentIndex}}
{{/each}} 

tested in Ember v1.1.0