module AbstractController::Helpers::ClassMethods

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

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

end
end
"#{bar} is the very best"
def foo(bar)
helper do
# Multi-line

helper { def hello() "Hello, world!" end }
# One line

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

helper 'resources/foo' # => requires 'resources/foo_helper' and includes Resources::FooHelper
helper :foo # => requires 'foo_helper' and includes FooHelper
in one of Rails' standard load paths:
when working with namespaced controllers, or other cases where the file containing the helper definition is not
and include the module in the template class. The second form illustrates how to include custom helpers
When the argument is a string or symbol, the method will provide the "_helper" suffix, require the file

helper FooHelper # => includes FooHelper
When the argument is a module it will be included directly in the template class.

* block - A block defining helper methods
* *args - Module, Symbol, String
==== Options

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

def helper(*args, &block)
  modules_for_helpers(args).each do |mod|
    add_template_helper(mod)
  end
  _helpers.module_eval(&block) if block_given?
end