ember-cli support for Handlebars @vars in each helper (i.e., @index, @key, @first, @last)

Question

I am getting a compilation error in ember-cli whenever I have a Handelbars template that uses @vars variables (i.e., @index, @key, @first, @last) inside of the each helper. (See http://handlebarsjs.com/#iteration for documentation on these @vars variables inside the each helper.) Below is a simple application built using ember-cli and containing only two files added to the program: routes/application.js and templates/application.hbs. At the bottom of this post is a screenshot of the compilation error message given by ember-cli. Is there an error in my code? Or is this a bug I should report on github @ https://github.com/stefanpenner/ember-cli?

routes/application.js

export default Ember.Route.extend({
    model: function() {
        return ['red', 'blue', 'green'];
    }
});

templates/application.hbs

{{#each model}}
  {{@index}}: {{this}}
{{/each}}

Screenshot of ember-cli compilation error message:

Here are the versions of the various tools involved:

• ember-cli: 0.0.40
• node: 0.10.30
• npm: 1.4.21
• Handlebars: 1.3.0
• Ember: 1.6.1

Answer 1

That really isn't related to ember-cli. Ember Handlebars doesn't support the @keyword items.

Answer 2

It's possible to mimic behavior of following Handlebars keywords: @index, @key, @first, @last.

@index

{{#each array as |item index|}}
  Index of item: `{{item}}` is: `{{index}}`
{{/each}}

@key

{{#each-in object as |key value|}}
  {{key}}: {{value}}
{{/each-in}}

@first

You could also mimic behavior of @first using ember-truth-helpers addon and taking advantage of eq helper - thanks to kristjan reinhold for this idea:

{{#each array as |item index|}}
  {{#if (eq index 0)}}
    <!-- first element specific html -->
  {{else}}
    <!-- other html -->
  {{/if}}
{{/each}}

Instead of (eq index 0) you can use (eq item array.firstObject).

@last

As dwickern suggested you can use Ember.Array.lastObject to mimic @last behavior.

{{#each array as |item|}}
  {{#if (eq item array.lastObject)}}
    <!-- last element specific html -->
  {{else}}
    <!-- other html -->
  {{/if}}
{{/each}}