Module: ActionController::Helpers::ClassMethods

Defined in:
lib/action_controller/helpers.rb

Overview

The template helpers serves to relieve the templates from including the same inline code again and again. It's a set of standardized methods for working with forms (FormHelper), dates (DateHelper), texts (TextHelper), and Active Records (ActiveRecordHelper) that's available to all templates by default.

It's also really easy to make your own helpers and it's much encouraged to keep the template files free from complicated logic. It's even encouraged to bundle common compositions of methods from other helpers (often the common helpers) as they're used by the specific application.

module MyHelper
  def hello_world() "hello world" end
end

MyHelper can now be included in a controller, like this:

class MyController < ActionController::Base
  helper :my_helper
end

…and, same as above, used in any template rendered from MyController, like this:

Let's hear what the helper has to say: <%= hello_world %>

Instance Method Summary collapse

Instance Method Details

#add_template_helper(helper_module) ⇒ Object

Makes all the (instance) methods in the helper module available to templates rendered through this controller. See ActionView::Helpers (classes/ActionView/Helpers.html) for more about making your own helper modules available to the templates.


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# File 'lib/action_controller/helpers.rb', line 47

def add_template_helper(helper_module) #:nodoc:
  master_helper_module.send(:include, helper_module)
end

#helper(*args, &block) ⇒ Object

Declare a helper:

helper :foo

requires 'foo_helper' and includes FooHelper in the template class.

helper FooHelper

includes FooHelper in the template class.

helper { def foo() "#{bar} is the very best" end }

evaluates the block in the template class, adding method #foo.

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

does all three.


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# File 'lib/action_controller/helpers.rb', line 60

def helper(*args, &block)
  args.flatten.each do |arg|
    case arg
      when Module
        add_template_helper(arg)
      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).to_a[1]
          msg = (requiree == file_name) ? "Missing helper file helpers/#{file_name}.rb" : "Can't load file: #{requiree}"
          raise LoadError.new(msg).copy_blame!(load_error)
        end

        add_template_helper(class_name.constantize)
      else
        raise ArgumentError, 'helper expects String, Symbol, or Module argument'
    end
  end

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

#helper_attr(*attrs) ⇒ Object

Declare a controller attribute as a helper. For example,

helper_attr :name
attr_accessor :name

makes the name and name= controller methods available in the view. The is a convenience wrapper for helper_method.


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# File 'lib/action_controller/helpers.rb', line 106

def helper_attr(*attrs)
  attrs.flatten.each { |attr| helper_method(attr, "#{attr}=") }
end

#helper_method(*methods) ⇒ Object

Declare a controller method as a helper. For example,

helper_method :link_to
def link_to(name, options) ... end

makes the link_to controller method available in the view.


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# File 'lib/action_controller/helpers.rb', line 91

def helper_method(*methods)
  methods.flatten.each do |method|
    master_helper_module.module_eval <<-end_eval
      def #{method}(*args, &block)
        controller.send(%(#{method}), *args, &block)
      end
    end_eval
  end
end