helper(*args, &block) — ActionController::Helpers::ClassMethods

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 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 }

Parameters

args rest
block block

Source

# File actionpack/lib/action_controller/helpers.rb, line 114
      def helper(*args, &block)
        args.flatten.each do |arg|
          case arg
            when Module
              add_template_helper(arg)
            when :all
              helper(all_application_helpers)
            when String, Symbol
              file_name  = arg.to_s.underscore + '_helper'
              class_name = file_name.camelize

              begin
                require_dependency(file_name)
              rescue LoadError => load_error
                requiree = / -- (.*?)(\.rb)?$/.match(load_error.message).to_a[1]
                if requiree == file_name
                  msg = "Missing helper file helpers/#{file_name}.rb"
                  raise LoadError.new(msg).copy_blame!(load_error)
                else
                  raise
                end
              end

              add_template_helper(class_name.constantize)
            else
              raise ArgumentError, "helper expects String, Symbol, or Module argument (was: #{args.inspect})"
          end
        end

        # Evaluate block in template class if given.
        master_helper_module.module_eval(&block) if block_given?
      end

Defined in actionpack/lib/action_controller/helpers.rb line 114 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActionController::Helpers::ClassMethods

Signature

Examples

Parameters