# Use handlebars.js templates with the asset pipeline and/or sprockets

Are your `handlebars.js` templates littering your Rails views with `script` tags? Wondering why the nifty Rails 3.1 asset pipeline streamlines all your JavaScript except for your Handlebars templates? Wouldn't it be nice to have your Handlebars templates compiled, compressed, and cached like your other JavaScript?

Yea, I think so too. That is why I wrote **handlebars_assets**. Give your Handlebars templates their own files (including partials) and have them compiled, compressed, and cached as part of the Rails 3.1 asset pipeline!

Using `sprockets` with Sinatra or another framework? **handlebars_assets** works outside of Rails too (as of v0.2.0)

# BREAKING CHANGE AS OF v0.9.0

My pull request to allow `/` in partials was pulled into Handlebars. The hack that converted partial names to underscored paths (`shared/_time` -> `_shared_time`) is no longer necessary and has been removed. You should change all the partial references in your app when upgrading from a version prior to v0.9.0.

# Version of handlebars.js

`handlebars_assets` is packaged with the current stable release of `handlebars.js`. See the section on using another version if that does not work for you.

# Installation

## Rails 4.0+

Load `handlebars_assets` in your `Gemfile`

```ruby
gem 'handlebars_assets'
```

Then follow [Javascript Setup](#javascript-setup)

Side Note: _As of Rails 4.0, the `assets` group is not supported in the Gemfile ([source](http://edgeguides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-3-2-to-rails-4-0-gemfile))._

## Rails 3.1+

Load `handlebars_assets` in your `Gemfile` as part of the `assets` group

```ruby
group :assets do
  gem 'handlebars_assets'
end
```

Then follow [Javascript Setup](#javascript-setup)

## Sprockets (Non-Rails)

`handlebars_assets` can work with earlier versions of Rails or other frameworks like Sinatra.

Load `handlebars_assets` in your `Gemfile`

```ruby
gem 'handlebars_assets'
```

Add the `HandlebarsAssets.path` to your `Sprockets::Environment` instance. This
lets Sprockets know where the Handlebars JavaScript files are and is required
for the next steps to work.

```ruby
env = Sprockets::Environment.new

require 'handlebars_assets'
env.append_path HandlebarsAssets.path
```

## Javascript Setup

Require `handlebars.runtime.js` in your JavaScript manifest (i.e. `application.js`)

```javascript
//= require handlebars.runtime
```

If you need to compile your JavaScript templates in the browser as well, you should instead require `handlebars.js` (which is significantly larger)

```javascript
//= require handlebars
```

### Templates directory

Generally you want to locate your template with your other assets, for example `app/assets/javascripts/templates`. In your JavaScript manifest file, use `require_tree` to pull in the templates

> app/assets/javascripts/application.js
```javascript
//= require_tree ./templates
```
This must be done before `//= require_tree .` otherwise all your templates will not have the intended prefix; and after your inclusion of handlebars/handlebars runtime.

## Rails Asset Precompiling

`handlebars_assets` also works when you are precompiling your assets.

### `rake assets:precompile`

If you are using `rake assets:precompile`, you have to re-run the `rake` command to rebuild any changed templates. See the [Rails guide](http://guides.rubyonrails.org/asset_pipeline.html#precompiling-assets) for more details.

### Heroku & other cloud hosts

If you are deploying to Heroku, be sure to read the [Rails guide](http://guides.rubyonrails.org/asset_pipeline.html#precompiling-assets) and in your `config/application.rb` set:

```ruby
config.assets.initialize_on_precompile = false
```

This avoids running your initializers when compiling assets (see the [guide](http://guides.rubyonrails.org/asset_pipeline.html#precompiling-assets) for why you would want that).

However, that does mean that you cannot set your configuration in an initializer. This [issue](https://github.com/leshill/handlebars_assets/issues/34) has a workaround, or you can set:

```ruby
config.assets.initialize_on_precompile = true
```

This will run all your initializers before precompiling assets.

# Usage

## The template files

Write your Handlebars templates as standalone files in your templates directory. Organize the templates similarly to Rails views.

For example, if you have new, edit, and show templates for a Contact model

```
templates/
  contacts/
    new.hbs
    edit.hbs
    show.hbs
```

Your file extensions tell the asset pipeline how to process the file. Use `.hbs` to compile the template with Handlebars.

If your file is `templates/contacts/new.hbs`, the asset pipeline will generate JavaScript code

1. Compile the Handlebars template to JavaScript code
1. Add the template code to the `HandlebarsTemplates` global under the name `contacts/new`

You can then invoke the resulting template in your application's JavaScript

NOTE: There will be no javascript object `HandlebarsTemplates` unless at least ONE template is included.

```javascript
HandlebarsTemplates['contacts/new'](context);
```

## Partials

If you begin the name of the template with an underscore, it will be recognized as a partial. You can invoke partials inside a template using the Handlebars partial syntax:

```
Invoke a {{> path/to/_partial }}
```

# Configuration

## The template namespace

By default, the global JavaScript object that holds the compiled templates is `HandlebarsTemplates`, but it can
be easily renamed. Another common template namespace is `JST`.  Just change the `template_namespace` configuration option
when you initialize your application.

```ruby
HandlebarsAssets::Config.template_namespace = 'JST'
```

## Ember Support

To compile your templates for use with [Ember.js](http://emberjs.com)
simply turn on the config option:

```ruby
HandlebarsAssets::Config.ember = true
```

If you need to compile templates for Ember and another framework then enable
multiple frameworks:

```ruby
HandlebarsAssets::Config.multiple_frameworks = true
```

After `mutliple_frameworks` has been enabled templates with the `.ember.hbs`
extension will be made available to Ember.

## `.hamlbars` and `.slimbars` Support

If you name your templates with the extension `.hamlbars`, you can use Haml syntax for your markup! Use `HandlebarsAssets::Config.haml_options` to pass custom options to the Haml rendering engine.

For example, if you have a file `widget.hamlbars` that looks like this:

```haml
%h1 {{title}}
%p {{body}}
```

The Haml will be pre-processed so that the Handlebars template is basically this:

```html
<h1> {{title}} </h1>
<p> {{body}} </p>
```

The same applies to `.slimbars` and the Slim gem. Use `HandlebarsAssets::Config.slim_options` to pass custom options to the Slim rendering engine.

<strong>Note:</strong> To use the `hb` handlebars helper with Haml, you'll also need to include the Hamlbars gem in your Gemfile:

```ruby
  gem 'hamlbars', '~> 2.0'
```

This will then allow you to do things like Haml blocks:

```haml
%ul.authors
= hb 'each authors' do
  %li<
    = succeed ',' do
      = hb 'lastName'
    = hb 'firstName'
```

Reference [hamlbars](https://github.com/jamesotron/hamlbars) for more information.

## Using another version of `handlebars.js`

Occasionally you might need to use a version of `handlebars.js` other than the included version. You can set the `compiler_path` and `compiler` options to use a custom version of `handlebars.js`.

```ruby
HandlebarsAssets::Config.compiler = 'my_handlebars.js' # Change the name of the compiler file
HandlebarsAssets::Config.compiler_path = Rails.root.join('app/assets/javascripts') # Change the location of the compiler file
```

## Patching `handlebars.js`

If you need specific customizations to the `handlebars.js` compiler, you can use patch the compiler with your own JavaScript patches.

The patch file(s) are concatenated with the `handlebars.js` file before compiling. Take a look at the test for details.

```ruby
HandlebarsAssets::Config.patch_files = 'my_patch.js'
HandlebarsAssets::Config.patch_path = Rails.root.join('app/assets/javascripts') # Defaults to `Config.compiler_path`
```

# Thanks

This gem is standing on the shoulders of giants.

Thank you Yehuda Katz (@wycats) for [handlebars.js](https://github.com/wycats/handlebars.js) and lots of other code I use every day.

Thank you Charles Lowell (@cowboyd) for [therubyracer](https://github.com/cowboyd/therubyracer) and [handlebars.rb](https://github.com/cowboyd/handlebars.rb).

# Maintainer

This gem is maintained by Alex Riedler [Github](https://github.com/AlexRiedler).

# Author

Les Hill, follow me on [Github](https://github.com/leshill) and [Twitter](https://twitter.com/leshill).

# Contributors

* Matt Burke         (@spraints)       : execjs support
*                    (@kendagriff)     : 1.8.7 compatibility
* Thorben Schröder   (@walski)         : 3.1 asset group for precompile
* Erwan Barrier      (@erwanb)         : Support for plain sprockets
* Brendan Loudermilk (@bloudermilk)    : HandlebarsAssets.path
* Dan Evans          (@danevans)       : Rails 2 support
* Ben Woosley        (@empact)         : Update to handlebars.js 1.0.0.beta.6
*                    (@cw-moshe)       : Remove 'templates/' from names
* Spike Brehm        (@spikebrehm)     : Config.template\_namespace option
* Ken Mayer          (@kmayer)         : Quick fix for template\_namespace option
* Brad Murray        (@wyaeld)         : Generic options support
* Blake Williams     (@BlakeWilliams)  : .handlebars extension
* Tristan Koch       (@trkoch)         : Strip leading whitespace from compiled templates
* Brian Cardarella   (@bcardarella)    : Ember support
* David Lee          (@davidlee)       : Slim support
* Phil Cohen         (@phlipper)       : README cleanup
* Akshay Rawat       (@akshayrawat)    : Update to handlebars.js 1.0.0-rc.3
* Turadg Aleahmad    (@turadg)         : Update to handlebars 1.0.0-rc.4
* Mark Rushakoff     (@mark-rushakoff) : Synchronize Sprockets engine registers with Rails
* Alex Riedler       (@AlexRiedler)    : Pass scope and locals up the chain
* lee                (@lee)            : Update to handlebars 1.0.0
* Ken Collins        (@metaskills)     : Register with Sprockets
* Blake Hitchcock    (@rbhitchcock)    : Support ember and other handlebars use simultaneously
* ajk                (@Darep)          : Fix .hbs extension for multi-framework support
*                    (@mattmenefee)    : README section for `hamlbars`
* Parker Selbert     (@sorentwo)       : README section for `multiple_frameworks`
* Francisco QV       (@panchoqv)       : README clarification
* Dylan Markow       (@dmarkow)        : README cleanup

# Contributing

Pull requests are welcome! Please do not update the version number.

In a nutshell:

1. Fork
1. Create a topic branch - git checkout -b my_branch
1. Push to your branch - git push origin my_branch
1. Create a Pull Request from your branch
1. That's it!