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require 'active_support/dependencies'
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# FIXME: helper { ... } is broken on Ruby 1.9
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module ActionController #:nodoc:
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module Helpers #:nodoc:
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def self.included(base)
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# Initialize the base module to aggregate its helpers.
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base.class_inheritable_accessor :master_helper_module
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base.master_helper_module = Module.new
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# Set the default directory for helpers
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base.class_inheritable_accessor :helpers_dir
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base.helpers_dir = (defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/app/helpers" : "app/helpers")
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# Extend base with class methods to declare helpers.
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base.extend(ClassMethods)
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# Wrap inherited to create a new master helper module for subclasses.
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alias_method_chain :inherited, :helper
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# The Rails framework provides a large number of helpers for working with +assets+, +dates+, +forms+,
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# +numbers+ and Active Record objects, to name a few. These helpers are available to all templates
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# In addition to using the standard template helpers provided in the Rails framework, creating custom helpers to
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# extract complicated logic or reusable functionality is strongly encouraged. By default, the controller will
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# include a helper whose name matches that of the controller, e.g., <tt>MyController</tt> will automatically
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# include <tt>MyHelper</tt>.
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# Additional helpers can be specified using the +helper+ class method in <tt>ActionController::Base</tt> or any
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# controller which inherits from it.
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# The +to_s+ method from the Time class can be wrapped in a helper method to display a custom message if
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# the Time object is blank:
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# module FormattedTimeHelper
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# def format_time(time, format=:long, blank_message=" ")
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# time.blank? ? blank_message : time.to_s(format)
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# FormattedTimeHelper can now be included in a controller, using the +helper+ class method:
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# class EventsController < ActionController::Base
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# helper FormattedTimeHelper
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# @events = Event.find(:all)
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# Then, in any view rendered by <tt>EventController</tt>, the <tt>format_time</tt> method can be called:
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# <% @events.each do |event| -%>
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# <% format_time(event.time, :short, "N/A") %> | <%= event.name %>
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# Finally, assuming we have two event instances, one which has a time and one which does not,
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# the output might look like this:
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# 23 Aug 11:30 | Carolina Railhawks Soccer Match
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# N/A | Carolina Railhaws Training Workshop
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# Makes all the (instance) methods in the helper module available to templates rendered through this controller.
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# See ActionView::Helpers (link:classes/ActionView/Helpers.html) for more about making your own helper modules
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# available to the templates.
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def add_template_helper(helper_module) #:nodoc:
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master_helper_module.module_eval { include helper_module }
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# The +helper+ class method can take a series of helper module names, a block, or both.
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# * <tt>*args</tt>: One or more modules, strings or symbols, or the special symbol <tt>:all</tt>.
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# * <tt>&block</tt>: A block defining helper methods.
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# When the argument is a string or symbol, the method will provide the "_helper" suffix, require the file
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# and include the module in the template class. The second form illustrates how to include custom helpers
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# when working with namespaced controllers, or other cases where the file containing the helper definition is not
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# in one of Rails' standard load paths:
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# helper :foo # => requires 'foo_helper' and includes FooHelper
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# helper 'resources/foo' # => requires 'resources/foo_helper' and includes Resources::FooHelper
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# When the argument is a module it will be included directly in the template class.
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# helper FooHelper # => includes FooHelper
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# When the argument is the symbol <tt>:all</tt>, the controller will include all helpers beneath
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# <tt>ActionController::Base.helpers_dir</tt> (defaults to <tt>app/helpers/**/*.rb</tt> under RAILS_ROOT).
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# Additionally, the +helper+ class method can receive and evaluate a block, making the methods defined available
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# helper { def hello() "Hello, world!" end }
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# "#{bar} is the very best"
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# Finally, all the above styles can be mixed together, and the +helper+ method can be invoked with a mix of
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# +symbols+, +strings+, +modules+ and blocks.
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# helper(:three, BlindHelper) { def mice() 'mice' end }
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def helper(*args, &block)
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args.flatten.each do |arg|
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add_template_helper(arg)
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helper(all_application_helpers)
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file_name = arg.to_s.underscore + '_helper'
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class_name = file_name.camelize
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require_dependency(file_name)
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rescue LoadError => load_error
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requiree = / -- (.*?)(\.rb)?$/.match(load_error.message).to_a[1]
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if requiree == file_name
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msg = "Missing helper file helpers/#{file_name}.rb"
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raise LoadError.new(msg).copy_blame!(load_error)
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add_template_helper(class_name.constantize)
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raise ArgumentError, "helper expects String, Symbol, or Module argument (was: #{args.inspect})"
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# Evaluate block in template class if given.
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master_helper_module.module_eval(&block) if block_given?
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# Declare a controller method as a helper. For example, the following
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# makes the +current_user+ controller method available to the view:
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# class ApplicationController < ActionController::Base
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# helper_method :current_user, :logged_in?
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# @current_user ||= User.find_by_id(session[:user])
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# current_user != nil
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# <% if logged_in? -%>Welcome, <%= current_user.name %><% end -%>
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def helper_method(*methods)
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methods.flatten.each do |method|
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master_helper_module.module_eval <<-end_eval
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def #{method}(*args, &block) # def current_user(*args, &block)
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controller.send(%(#{method}), *args, &block) # controller.send(%(current_user), *args, &block)
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# Declares helper accessors for controller attributes. For example, the
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# following adds new +name+ and <tt>name=</tt> instance methods to a
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# controller and makes them available to the view:
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# attr_accessor :name
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def helper_attr(*attrs)
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attrs.flatten.each { |attr| helper_method(attr, "#{attr}=") }
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# Provides a proxy to access helpers methods from outside the view.
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@helper_proxy = ActionView::Base.new
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@helper_proxy.extend master_helper_module
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def default_helper_module!
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module_name = name.sub(/Controller$|$/, 'Helper')
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module_path = module_name.split('::').map { |m| m.underscore }.join('/')
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require_dependency module_path
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helper module_name.constantize
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rescue MissingSourceFile => e
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raise unless e.is_missing? module_path
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rescue NameError => e
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raise unless e.missing_name? module_name
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def inherited_with_helper(child)
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inherited_without_helper(child)
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child.master_helper_module = Module.new
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child.master_helper_module.__send__ :include, master_helper_module
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child.__send__ :default_helper_module!
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rescue MissingSourceFile => e
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raise unless e.is_missing?("helpers/#{child.controller_path}_helper")
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# Extract helper names from files in app/helpers/**/*.rb
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def all_application_helpers
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extract = /^#{Regexp.quote(helpers_dir)}\/?(.*)_helper.rb$/
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Dir["#{helpers_dir}/**/*_helper.rb"].map { |file| file.sub extract, '\1' }