Module: ActionController::Helpers::ClassMethods

Module | ActionController::Helpers::ClassMethods
In: | 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="&nbsp;")
          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

### Methods

helper helper_attr helper_method helpers

### Public Instance methods

helper(*args, &block)

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 from `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 }

helper_attr(*attrs)

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

helper_method(*methods)

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 -%>

helpers()

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

[Validate]