ActionController::Helpers::ClassMethods

• actionpack/lib/action_controller/helpers.rb

The Rails framework provides a large number of helpers for working with assets, dates, forms, numbers and Active Record objects, to name a few. These helpers are available to all templates by default.

In addition to using the standard template helpers provided in the Rails framework, creating custom helpers to extract complicated logic or reusable functionality is strongly encouraged. By default, the controller will include a helper whose name matches that of the controller, e.g., MyController will automatically include MyHelper.

Additional helpers can be specified using the helper class method in ActionController::Base or any controller which inherits from it.

Examples

The to_s method from the Time class can be wrapped in a helper method to display a custom message if the Time object is blank:

  module FormattedTimeHelper
    def format_time(time, format=:long, blank_message=" ")
      time.blank? ? blank_message : time.to_s(format)
    end
  end

FormattedTimeHelper can now be included in a controller, using the helper class method:

  class EventsController < ActionController::Base
    helper FormattedTimeHelper
    def index
      @events = Event.find(:all)
    end
  end

Then, in any view rendered by EventController, the format_time method can be called:

  <% @events.each do |event| -%>
    <p>
      <% format_time(event.time, :short, "N/A") %> | <%= event.name %>
    </p>
  <% end -%>

Finally, assuming we have two event instances, one which has a time and one which does not, the output might look like this:

  23 Aug 11:30 | Carolina Railhawks Soccer Match
  N/A | Carolina Railhaws Training Workshop

• helper
• helper_attr
• helper_method
• helpers

The helper class method can take a series of helper module names, a block, or both.

• *args: One or more modules, strings or symbols, or the special symbol :all.
• &block: A block defining helper methods.

Examples

When the argument is a string or symbol, the method will provide the "_helper" suffix, require the file and include the module in the template class. The second form illustrates how to include custom helpers when working with namespaced controllers, or other cases where the file containing the helper definition is not in one of Rails’ standard load paths:

  helper :foo             # => requires 'foo_helper' and includes FooHelper
  helper 'resources/foo'  # => requires 'resources/foo_helper' and includes Resources::FooHelper

When the argument is a module it will be included directly in the template class.

  helper FooHelper # => includes FooHelper

When the argument is the symbol :all, the controller will include all helpers beneath ActionController::Base.helpers_dir (defaults to app/helpers/**/*.rb under RAILS_ROOT).

  helper :all

Additionally, the helper class method can receive and evaluate a block, making the methods defined available to the template.

  # One line
  helper { def hello() "Hello, world!" end }
  # Multi-line
  helper do
    def foo(bar)
      "#{bar} is the very best"
    end
  end

Finally, all the above styles can be mixed together, and the helper method can be invoked with a mix of symbols, strings, modules and blocks.

  helper(:three, BlindHelper) { def mice() 'mice' end }

Declares helper accessors for controller attributes. For example, the following adds new name and name= instance methods to a controller and makes them available to the view:

  helper_attr :name
  attr_accessor :name

Declare a controller method as a helper. For example, the following makes the current_user controller method available to the view:

  class ApplicationController < ActionController::Base
    helper_method :current_user, :logged_in?

    def current_user
      @current_user ||= User.find_by_id(session[:user])
    end

     def logged_in?
       current_user != nil
     end
  end

In a view:

 <% if logged_in? -%>Welcome, <%= current_user.name %><% end -%>

Provides a proxy to access helpers methods from outside the view.