require "active_support/dependencies"
module AbstractController
module Helpers
extend ActiveSupport::Concern
included do
class_attribute :_helpers
self._helpers = Module.new
class_attribute :_helper_methods
self._helper_methods = Array.new
end
class MissingHelperError < LoadError
def initialize(error, path)
@error = error
@path = "helpers/#{path}.rb"
set_backtrace error.backtrace
if error.path =~ /^#{path}(\.rb)?$/
super("Missing helper file helpers/%s.rb" % path)
else
raise error
end
end
end
module ClassMethods
# 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.
def inherited(klass)
helpers = _helpers
klass._helpers = Module.new { include helpers }
klass.class_eval { default_helper_module! } unless klass.anonymous?
super
end
# 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
# * <tt>method[, method]</tt> - A name or names of a method on the controller
# to be made available on the view.
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
# The +helper+ class method can take a series of helper module names, a block, or both.
#
# ==== Options
# * <tt>*args</tt> - Module, Symbol, String
# * <tt>block</tt> - A block defining helper methods
#
# 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 "_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
#
# 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 }
#
def helper(*args, &block)
modules_for_helpers(args).each do |mod|
add_template_helper(mod)
end
_helpers.module_eval(&block) if block_given?
end
# Clears up all existing helpers in this class, only keeping the helper
# with the same name as this class.
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
# Returns a list of modules, normalized from the acceptable kinds of
# helpers with the following behavior:
#
# String or Symbol:: :FooBar or "FooBar" becomes "foo_bar_helper",
# and "foo_bar_helper.rb" is loaded using require_dependency.
#
# Module:: No further processing
#
# After loading the appropriate files, the corresponding modules
# are returned.
#
# ==== Parameters
# * <tt>args</tt> - An array of helpers
#
# ==== Returns
# * <tt>Array</tt> - A normalized list of modules for the list of
# helpers provided.
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
private
# Makes all the (instance) methods in the helper module available to templates
# rendered through this controller.
#
# ==== Parameters
# * <tt>module</tt> - The module to include into the current helper module
# for the class
def add_template_helper(mod)
_helpers.module_eval { include mod }
end
def default_helper_module!
module_name = name.sub(/Controller$/, "".freeze)
module_path = module_name.underscore
helper module_path
rescue LoadError => e
raise e unless e.is_missing? "helpers/#{module_path}_helper"
rescue NameError => e
raise e unless e.missing_name? "#{module_name}Helper"
end
end
end
end
