Ruby on Rails latest stable (v5.2.3) - 0 notes - Class: ActionController::Helpers::ClassMethods

Method deprecated or moved

This method is deprecated or moved on the latest stable version. The last existing version (v2.3.8) is shown here.

These similar methods exist in v5.2.3:

helper(*args, &block) public

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.


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"

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 }
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