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Paloma

Page-specific javascript for Rails done right.

Advantages

Choose what specific javascript code to run per page.
Easily make ruby variables available on your javascript files.
Write in vanilla javascript, coffeescript, and anything that compiles to js.
No external JS library dependency.
Easy to understand (because it is patterned after Rails controller).

Minimum Requirement

Rails 4.0.2 or higher

Quick Example

Paloma controller:

Paloma.controller('Users', {
  new: function(){
    // Executes when Rails Users#new is executed.
    alert('Hello Sexy User!');
  }
});

Rails controller:

def UsersController < ApplicationController
  def new
    # no special method to call
    @user = User.new
  end
end

Install

Install gem.

Without bundler: sudo gem install paloma.
With bundler, add this to your Gemfile:
```
gem 'paloma', '~> 6.1.0'
```

Require paloma in your application.js:

//= require paloma

In your layouts, insert Paloma's hook. This is responsible for connecting your ruby code to your javascript code.

application.html.erb
```
<html>
   <head>
   </head>

   <body>
      <%= yield %>
      <%= insert_paloma_hook %>
   </body>
</html>
```
Start Paloma to initialize the appropriate controller and execute a certain action. Most of the time this will be inside document.ready.

$(document).ready(function(){
  Paloma.start();
});

Controller

Paloma controllers are javascript classes which will be mapped with your Rails controller. Basically, both Paloma and Rails controllers will share the same name.

It is created or accessed (if existing), using Paloma.controller method.

var ArticlesController = Paloma.controller('Articles');

Note: Using Paloma.controller method, you can access the same controller across different files.

Actions

To handle specific actions of your Rails controller, add methods to your Paloma controller's prototype.

var ArticlesController = Paloma.controller('Articles');

ArticlesController.prototype.edit = function(){
  // Handle edit article
};

Or you can pass the prototype value as the 2nd argument of the Paloma.controller method.

Paloma.controller('Articles', {
  edit: function(){
    // Handle edit article
  }
});

Namespace

Namespaced controller should follow the format namespace/controller.

Rails controller:

class Admin::UsersController < ApplicationController
  def new
    @user = User.new
  end
end

Paloma controller:

Paloma.controller('Admin/Users', {
  new: function(){
    // Handle new admin user
  }
});

Controller Inheritance

Controller inheritance is accomplished using the syntax Controller < ParentController (same as ruby's syntax).

Parent:

Paloma.controller('Application', {
  index: function(){
    alert('Application: Index');
  },

  new: function(){
    alert('Application: New');
  }
});

Child:

Paloma.controller('Users < Application', {
  // Override Application's new action
  new: function(){
    alert('Users: New');
  }
});

Before Callbacks

Executing a method before doing an action can be done using the before property of a controller.

Paloma.controller('Articles', {
  before: ['show -> alert'],

  show: function(){
    // Handle show Article
  },

  alert: function(){
    alert("You are about to show an article.");
  }
});

Multiple actions and callbacks should be separated by spaces. The callbacks order on the string will define the order of their execution. So in this case, alert will be executed first before log.

Paloma.controller('Articles', {
  before: ['show index -> alert log'],

  index: function(){},
  show: function(){},

  alert: function(){
    alert('Before index and show');
  },

  log: function(){
    console.log('Before index and show');
  }
});

Multiple Before Entries

The order of execution is also based on the order of entries on the before array.

Paloma.controller('Articles', {
  before: [
    'show -> beforeShow',
    'index -> beforeIndex',
    'show index -> beforeShowAndIndex'
  ],

  beforeShow: function(){ alert('Before Show'); },
  beforeShowAndIndex: function(){ alert('Before Show and Index'); }
});

When show is executed, the following callbacks will be called in this order: beforeShow then beforeShowAndIndex.

Before All Actions

all is a special string that can be used to indicate a catch-all callback.

Paloma.controller('Articles', {
  before: ['all -> initialize'],

  initialize: function(){
    alert('execute before every action');
  }
});

Execution Details

You can access what controller and action Paloma is about to execute or already executed, by accessing the controller and action property of a Paloma controller.

Paloma.controller('Users', {
  before: ['all -> log'],

  log: function(){
    console.log('Controller: ' + this.controller);
    console.log('Action: ' + this.action);
  }
})

Advanced Usage

You can manipulate what controller/action should Paloma execute by calling js method before rendering.

Changing controller.

class UsersController < ApplicationController
  def new
    @user = User.new

    # will use Accounts controller instead of Users controller
    js 'Accounts'
  end
end

Changing action.

You can use the symbol syntax:

def new
  @user = User.new

  # will execute register method instead of new
  js :register
end

Or the string syntax:

def new
  @user = User.new

  # will execute register method instead of new
  js '#register'
end

Changing controller and action.

def new
  @user = User.new

  # will execute Accounts#register instead of Users#new
  js 'Accounts#register'
end

Changing controller and action with namespace.

def new
  @user = User.new

  # will use Admin/Accounts instead of Users controller
  js `Admin/Accounts`
end

def new
  @user = User.new

  # will execute Admin/Accounts#register instead of Users#new
  js 'Admin/Accounts#register'
end

Passing Parameters

You can pass parameters to your Paloma Controller in two ways.

Passing a hash. (parameters only)

def show
  user = User.find params[:id]

  js :id => user.id, :myParam => 'test'
end

Passing a namespace/controller#action string and a hash.

def show
  user = User.find params[:id]

  js 'Admin/Users', :id => user.id, :myParam => 'test'
end

You can access the passed parameters using the params property of your Paloma controller.

Paloma.controller('Users', {
  show: function(){
    alert("User id: " + this.params.id);
    alert("String: " + this.params.myParam);
  }
});

Preventing Paloma Execution

If you do not want Paloma to execute in a specific Rails Controller action you pass false to the js method.

def edit
  @user = User.find params[:id]
  js false
end

Controller-wide Setup

You can call js outside Rails controller actions for controller-wide settings.

Example:

class UsersController < ApplicationController

  # use Accounts controller instead of Users for all actions.
  js 'Accounts'

end

Like before_action of Rails you can also pass only and except options.

class UsersController < ApplicationController

  # Use Admin/Accounts except for show and destroy method
  js 'Admin/Accounts', :except => [:show, :destroy]

end

IMPORTANT NOTE: If you are going to pass parameters for Controller-wide settings, pass a hash using the :params key.

class UsersController < ApplicationController
  js 'Accounts', :params => {:x => 1, :y => 2, :z => 3}, :only => :show
end

Overriding Controller-wide Setup

If you want to override the controller-wide setup call js again inside a controller action. From there, you can override the controller/action or pass additional parameters.

class UsersController < ApplicationController
  js 'Accounts', :params => {:x => 1}

  def new
    @user = User.new

    # will execute Accounts#register with params {:x => 1, :y => 2}
    js :register, :y => 2
  end
end

Hook

insert_paloma_hook is a helper method that you use in your views to insert Paloma's HTML hook. It is what connects your ruby code to your javascript code. Basically, it contains a javascript code that has embedded ruby in it. That javascript code will register the Rails controller and action to Paloma's engine.

Ideally, you just need to call insert_paloma_hook in your layouts, since the layout will always be included in every rendered view. But if you are rendering a view without a layout, make sure to call insert_paloma_hook in that view.

Testing

A helper module Paloma::TestHelper is provided to help with testing parameters passed to javascript in a controller test. This module exposes a js_params method which returns the set of parameters passed to paloma, which you can then make assertions on.

For example:

class UsersController
  def show
    user = User.find params[:id]

    js :id => user.id, :myParam => 'test'
  end
end

Corresponding test (Minitest):

# Require test helper
require "paloma/test_helper"

class UsersControler < ActiveSupport::TestCase
  # Include helper to access `js_params` method
  include Paloma::TestHelper

  test "should get show" do
    user = User.create!
    get :show, id: user.id
    
    expected_params = { id: user.id, myParam: 'test' }
    assert_equal(expected_params, js_params)
  end
end

Starting Paloma

Once Paloma's HTML hook is already executed, you can now start Paloma by calling Paloma.start() in your javascript code. First, it will execute the HTML hook if not yet executed, then will initialize the correct Paloma controller, execute any before callbacks, and finally execute the correct action if available.

AJAX

Make sure that the AJAX response contains the HTML hook. (use insert_paloma_hook)

Start Paloma on complete/success.

$.get('http://example.com', function(response){
   $('#result').html(response);
   Paloma.start();
});

Turbolinks Support

Execute Paloma when user hits `Back` or `Forward` button.

Paloma executes page-specific javascript by adding a <script> tag to the response body. Turbolinks, by default, executes any inline javascript in the response body when you visit a page, so the <script> tag appended by Paloma will automatically be executed. However, when Turbolinks restores a page from cache (this happens when a user hits Back or Forward button in his browser) any inline javascript will not be executed anymore. This is the intentional behavior of Turbolinks, and it is not a bug. If you want to execute Paloma again when Turbolinks restores a page, do something like this:

$(document).on('page:restore', function(){
  Paloma.start();
});