Methods

Instance Public methods

clear_helpers()

Clears up all existing helpers in this class, only keeping the helper with the same name as this class.

๐Ÿ“ Source code 
# File actionpack/lib/abstract_controller/helpers.rb, line 117
      def clear_helpers
        inherited_helper_methods = _helper_methods
        self._helpers = Module.new
        self._helper_methods = Array.new

        inherited_helper_methods.each { |meth| helper_method meth }
        default_helper_module! unless anonymous?
      end
๐Ÿ”Ž See on GitHub

helper(*args, &block)

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

Options

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

helper FooHelper # => includes FooHelper

When the argument is a string or symbol, the method will provide the โ€œ_helperโ€ 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

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 }
๐Ÿ“ Source code 
# File actionpack/lib/abstract_controller/helpers.rb, line 107
      def helper(*args, &block)
        modules_for_helpers(args).each do |mod|
          add_template_helper(mod)
        end

        _helpers.module_eval(&block) if block_given?
      end
๐Ÿ”Ž See on GitHub

helper_method(*meths)

Declare a controller method as a helper. For example, the following makes the current_user and logged_in? controller methods 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 -%>

Parameters

  • method[, method] - A name or names of a method on the controller to be made available on the view.

๐Ÿ“ Source code 
# File actionpack/lib/abstract_controller/helpers.rb, line 60
      def helper_method(*meths)
        meths.flatten!
        self._helper_methods += meths

        meths.each do |meth|
          _helpers.class_eval <<-ruby_eval, __FILE__, __LINE__ + 1
            def #{meth}(*args, &blk)                               # def current_user(*args, &blk)
              controller.send(%(#{meth}), *args, &blk)             #   controller.send(:current_user, *args, &blk)
            end                                                    # end
          ruby_eval
        end
      end
๐Ÿ”Ž See on GitHub

inherited(klass)

When a class is inherited, wrap its helper module in a new module. This ensures that the parent class's module can be changed independently of the child class's.

๐Ÿ“ Source code 
# File actionpack/lib/abstract_controller/helpers.rb, line 32
      def inherited(klass)
        helpers = _helpers
        klass._helpers = Module.new { include helpers }
        klass.class_eval { default_helper_module! } unless klass.anonymous?
        super
      end
๐Ÿ”Ž See on GitHub

modules_for_helpers(args)

Returns a list of modules, normalized from the acceptable kinds of helpers with the following behavior:

String or Symbol

:FooBar or โ€œFooBarโ€ becomes โ€œfoo_bar_helperโ€,

and โ€œfoo_bar_helper.rbโ€ is loaded using require_dependency.

Module

No further processing

After loading the appropriate files, the corresponding modules are returned.

Parameters

  • args - An array of helpers

Returns

  • Array - A normalized list of modules for the list of helpers provided.

๐Ÿ“ Source code 
# File actionpack/lib/abstract_controller/helpers.rb, line 143
      def modules_for_helpers(args)
        args.flatten.map! do |arg|
          case arg
          when String, Symbol
            file_name = "#{arg.to_s.underscore}_helper"
            begin
              require_dependency(file_name)
            rescue LoadError => e
              raise AbstractController::Helpers::MissingHelperError.new(e, file_name)
            end

            mod_name = file_name.camelize
            begin
              mod_name.constantize
            rescue LoadError
              # dependencies.rb gives a similar error message but its wording is
              # not as clear because it mentions autoloading. To the user all it
              # matters is that a helper module couldn't be loaded, autoloading
              # is an internal mechanism that should not leak.
              raise NameError, "Couldn't find #{mod_name}, expected it to be defined in helpers/#{file_name}.rb"
            end
          when Module
            arg
          else
            raise ArgumentError, "helper must be a String, Symbol, or Module"
          end
        end
      end
๐Ÿ”Ž See on GitHub