form_options_helper.rb

require 'cgi'
require 'erb'
require 'action_view/helpers/form_helper'
require 'active_support/core_ext/object/blank'
require 'active_support/core_ext/string/output_safety'

module ActionView
  # = Action View Form Option Helpers
  module Helpers
    # Provides a number of methods for turning different kinds of containers into a set of option tags.
    # == Options
    # The <tt>collection_select</tt>, <tt>select</tt> and <tt>time_zone_select</tt> methods take an <tt>options</tt> parameter, a hash:
    #
    # * <tt>:include_blank</tt> - set to true or a prompt string if the first option element of the select element is a blank. Useful if there is not a default value required for the select element.
    #
    # For example,
    #
    #   select("post", "category", Post::CATEGORIES, {:include_blank => true})
    #
    # could become:
    #
    #   <select name="post[category]">
    #     <option></option>
    #     <option>joke</option>
    #     <option>poem</option>
    #   </select>
    #
    # Another common case is a select tag for an <tt>belongs_to</tt>-associated object.
    #
    # Example with @post.person_id => 2:
    #
    #   select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, {:include_blank => 'None'})
    #
    # could become:
    #
    #   <select name="post[person_id]">
    #     <option value="">None</option>
    #     <option value="1">David</option>
    #     <option value="2" selected="selected">Sam</option>
    #     <option value="3">Tobias</option>
    #   </select>
    #
    # * <tt>:prompt</tt> - set to true or a prompt string. When the select element doesn't have a value yet, this prepends an option with a generic prompt -- "Please select" -- or the given prompt string.
    #
    # Example:
    #
    #   select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, {:prompt => 'Select Person'})
    #
    # could become:
    #
    #   <select name="post[person_id]">
    #     <option value="">Select Person</option>
    #     <option value="1">David</option>
    #     <option value="2">Sam</option>
    #     <option value="3">Tobias</option>
    #   </select>
    #
    # Like the other form helpers, +select+ can accept an <tt>:index</tt> option to manually set the ID used in the resulting output. Unlike other helpers, +select+ expects this
    # option to be in the +html_options+ parameter.
    #
    # Example:
    #
    #   select("album[]", "genre", %w[rap rock country], {}, { :index => nil })
    #
    # becomes:
    #
    #   <select name="album[][genre]" id="album__genre">
    #     <option value="rap">rap</option>
    #     <option value="rock">rock</option>
    #     <option value="country">country</option>
    #   </select>
    #
    # * <tt>:disabled</tt> - can be a single value or an array of values that will be disabled options in the final output.
    #
    # Example:
    #
    #   select("post", "category", Post::CATEGORIES, {:disabled => 'restricted'})
    #
    # could become:
    #
    #   <select name="post[category]">
    #     <option></option>
    #     <option>joke</option>
    #     <option>poem</option>
    #     <option disabled="disabled">restricted</option>
    #   </select>
    #
    # When used with the <tt>collection_select</tt> helper, <tt>:disabled</tt> can also be a Proc that identifies those options that should be disabled.
    #
    # Example:
    #
    #   collection_select(:post, :category_id, Category.all, :id, :name, {:disabled => lambda{|category| category.archived? }})
    #
    # If the categories "2008 stuff" and "Christmas" return true when the method <tt>archived?</tt> is called, this would return:
    #   <select name="post[category_id]">
    #     <option value="1" disabled="disabled">2008 stuff</option>
    #     <option value="2" disabled="disabled">Christmas</option>
    #     <option value="3">Jokes</option>
    #     <option value="4">Poems</option>
    #   </select>
    #
    module FormOptionsHelper
      # ERB::Util can mask some helpers like textilize. Make sure to include them.
      include TextHelper

      # Create a select tag and a series of contained option tags for the provided object and method.
      # The option currently held by the object will be selected, provided that the object is available.
      #
      # There are two possible formats for the choices parameter, corresponding to other helpers' output:
      #   * A flat collection: see options_for_select
      #   * A nested collection: see grouped_options_for_select
      #
      # Example with @post.person_id => 1:
      #   select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, { :include_blank => true })
      #
      # could become:
      #
      #   <select name="post[person_id]">
      #     <option value=""></option>
      #     <option value="1" selected="selected">David</option>
      #     <option value="2">Sam</option>
      #     <option value="3">Tobias</option>
      #   </select>
      #
      # This can be used to provide a default set of options in the standard way: before rendering the create form, a
      # new model instance is assigned the default options and bound to @model_name. Usually this model is not saved
      # to the database. Instead, a second model object is created when the create request is received.
      # This allows the user to submit a form page more than once with the expected results of creating multiple records.
      # In addition, this allows a single partial to be used to generate form inputs for both edit and create forms.
      #
      # By default, <tt>post.person_id</tt> is the selected option. Specify <tt>:selected => value</tt> to use a different selection
      # or <tt>:selected => nil</tt> to leave all options unselected. Similarly, you can specify values to be disabled in the option
      # tags by specifying the <tt>:disabled</tt> option. This can either be a single value or an array of values to be disabled.
      #
      # ==== Gotcha
      #
      # The HTML specification says when +multiple+ parameter passed to select and all options got deselected
      # web browsers do not send any value to server. Unfortunately this introduces a gotcha:
      # if an +User+ model has many +roles+ and have +role_ids+ accessor, and in the form that edits roles of the user
      # the user deselects all roles from +role_ids+ multiple select box, no +role_ids+ parameter is sent. So,
      # any mass-assignment idiom like
      #
      #   @user.update_attributes(params[:user])
      #
      # wouldn't update roles.
      #
      # To prevent this the helper generates an auxiliary hidden field before
      # every multiple select. The hidden field has the same name as multiple select and blank value.
      #
      # This way, the client either sends only the hidden field (representing
      # the deselected multiple select box), or both fields. Since the HTML specification
      # says key/value pairs have to be sent in the same order they appear in the
      # form, and parameters extraction gets the last occurrence of any repeated
      # key in the query string, that works for ordinary forms.
      #
      def select(object, method, choices, options = {}, html_options = {})
        Tags::Select.new(object, method, self, choices, options, html_options).render
      end

      # Returns <tt><select></tt> and <tt><option></tt> tags for the collection of existing return values of
      # +method+ for +object+'s class. The value returned from calling +method+ on the instance +object+ will
      # be selected. If calling +method+ returns +nil+, no selection is made without including <tt>:prompt</tt>
      # or <tt>:include_blank</tt> in the +options+ hash.
      #
      # The <tt>:value_method</tt> and <tt>:text_method</tt> parameters are methods to be called on each member
      # of +collection+. The return values are used as the +value+ attribute and contents of each
      # <tt><option></tt> tag, respectively. They can also be any object that responds to +call+, such
      # as a +proc+, that will be called for each member of the +collection+ to
      # retrieve the value/text.
      #
      # Example object structure for use with this method:
      #   class Post < ActiveRecord::Base
      #     belongs_to :author
      #   end
      #   class Author < ActiveRecord::Base
      #     has_many :posts
      #     def name_with_initial
      #       "#{first_name.first}. #{last_name}"
      #     end
      #   end
      #
      # Sample usage (selecting the associated Author for an instance of Post, <tt>@post</tt>):
      #   collection_select(:post, :author_id, Author.all, :id, :name_with_initial, :prompt => true)
      #
      # If <tt>@post.author_id</tt> is already <tt>1</tt>, this would return:
      #   <select name="post[author_id]">
      #     <option value="">Please select</option>
      #     <option value="1" selected="selected">D. Heinemeier Hansson</option>
      #     <option value="2">D. Thomas</option>
      #     <option value="3">M. Clark</option>
      #   </select>
      def collection_select(object, method, collection, value_method, text_method, options = {}, html_options = {})
        Tags::CollectionSelect.new(object, method, self, collection, value_method, text_method, options, html_options).render
      end

      # Returns <tt><select></tt>, <tt><optgroup></tt> and <tt><option></tt> tags for the collection of existing return values of
      # +method+ for +object+'s class. The value returned from calling +method+ on the instance +object+ will
      # be selected. If calling +method+ returns +nil+, no selection is made without including <tt>:prompt</tt>
      # or <tt>:include_blank</tt> in the +options+ hash.
      #
      # Parameters:
      # * +object+ - The instance of the class to be used for the select tag
      # * +method+ - The attribute of +object+ corresponding to the select tag
      # * +collection+ - An array of objects representing the <tt><optgroup></tt> tags.
      # * +group_method+ - The name of a method which, when called on a member of +collection+, returns an
      #   array of child objects representing the <tt><option></tt> tags.
      # * +group_label_method+ - The name of a method which, when called on a member of +collection+, returns a
      #   string to be used as the +label+ attribute for its <tt><optgroup></tt> tag.
      # * +option_key_method+ - The name of a method which, when called on a child object of a member of
      #   +collection+, returns a value to be used as the +value+ attribute for its <tt><option></tt> tag.
      # * +option_value_method+ - The name of a method which, when called on a child object of a member of
      #   +collection+, returns a value to be used as the contents of its <tt><option></tt> tag.
      #
      # Example object structure for use with this method:
      #   class Continent < ActiveRecord::Base
      #     has_many :countries
      #     # attribs: id, name
      #   end
      #   class Country < ActiveRecord::Base
      #     belongs_to :continent
      #     # attribs: id, name, continent_id
      #   end
      #   class City < ActiveRecord::Base
      #     belongs_to :country
      #     # attribs: id, name, country_id
      #   end
      #
      # Sample usage:
      #   grouped_collection_select(:city, :country_id, @continents, :countries, :name, :id, :name)
      #
      # Possible output:
      #   <select name="city[country_id]">
      #     <optgroup label="Africa">
      #       <option value="1">South Africa</option>
      #       <option value="3">Somalia</option>
      #     </optgroup>
      #     <optgroup label="Europe">
      #       <option value="7" selected="selected">Denmark</option>
      #       <option value="2">Ireland</option>
      #     </optgroup>
      #   </select>
      #
      def grouped_collection_select(object, method, collection, group_method, group_label_method, option_key_method, option_value_method, options = {}, html_options = {})
        Tags::GroupedCollectionSelect.new(object, method, self, collection, group_method, group_label_method, option_key_method, option_value_method, options, html_options).render
      end

      # Return select and option tags for the given object and method, using
      # #time_zone_options_for_select to generate the list of option tags.
      #
      # In addition to the <tt>:include_blank</tt> option documented above,
      # this method also supports a <tt>:model</tt> option, which defaults
      # to ActiveSupport::TimeZone. This may be used by users to specify a
      # different time zone model object. (See +time_zone_options_for_select+
      # for more information.)
      #
      # You can also supply an array of ActiveSupport::TimeZone objects
      # as +priority_zones+, so that they will be listed above the rest of the
      # (long) list. (You can use ActiveSupport::TimeZone.us_zones as a convenience
      # for obtaining a list of the US time zones, or a Regexp to select the zones
      # of your choice)
      #
      # Finally, this method supports a <tt>:default</tt> option, which selects
      # a default ActiveSupport::TimeZone if the object's time zone is +nil+.
      #
      # Examples:
      #   time_zone_select( "user", "time_zone", nil, :include_blank => true)
      #
      #   time_zone_select( "user", "time_zone", nil, :default => "Pacific Time (US & Canada)" )
      #
      #   time_zone_select( "user", 'time_zone', ActiveSupport::TimeZone.us_zones, :default => "Pacific Time (US & Canada)")
      #
      #   time_zone_select( "user", 'time_zone', [ ActiveSupport::TimeZone['Alaska'], ActiveSupport::TimeZone['Hawaii'] ])
      #
      #   time_zone_select( "user", 'time_zone', /Australia/)
      #
      #   time_zone_select( "user", "time_zone", ActiveSupport::TimeZone.all.sort, :model => ActiveSupport::TimeZone)
      def time_zone_select(object, method, priority_zones = nil, options = {}, html_options = {})
        Tags::TimeZoneSelect.new(object, method, self, priority_zones, options, html_options).render
      end

      # Accepts a container (hash, array, enumerable, your type) and returns a string of option tags. Given a container
      # where the elements respond to first and last (such as a two-element array), the "lasts" serve as option values and
      # the "firsts" as option text. Hashes are turned into this form automatically, so the keys become "firsts" and values
      # become lasts. If +selected+ is specified, the matching "last" or element will get the selected option-tag. +selected+
      # may also be an array of values to be selected when using a multiple select.
      #
      # Examples (call, result):
      #   options_for_select([["Dollar", "$"], ["Kroner", "DKK"]])
      #     <option value="$">Dollar</option>\n<option value="DKK">Kroner</option>
      #
      #   options_for_select([ "VISA", "MasterCard" ], "MasterCard")
      #     <option>VISA</option>\n<option selected="selected">MasterCard</option>
      #
      #   options_for_select({ "Basic" => "$20", "Plus" => "$40" }, "$40")
      #     <option value="$20">Basic</option>\n<option value="$40" selected="selected">Plus</option>
      #
      #   options_for_select([ "VISA", "MasterCard", "Discover" ], ["VISA", "Discover"])
      #     <option selected="selected">VISA</option>\n<option>MasterCard</option>\n<option selected="selected">Discover</option>
      #
      # You can optionally provide html attributes as the last element of the array.
      #
      # Examples:
      #   options_for_select([ "Denmark", ["USA", {:class => 'bold'}], "Sweden" ], ["USA", "Sweden"])
      #     <option value="Denmark">Denmark</option>\n<option value="USA" class="bold" selected="selected">USA</option>\n<option value="Sweden" selected="selected">Sweden</option>
      #
      #   options_for_select([["Dollar", "$", {:class => "bold"}], ["Kroner", "DKK", {:onclick => "alert('HI');"}]])
      #     <option value="$" class="bold">Dollar</option>\n<option value="DKK" onclick="alert('HI');">Kroner</option>
      #
      # If you wish to specify disabled option tags, set +selected+ to be a hash, with <tt>:disabled</tt> being either a value
      # or array of values to be disabled. In this case, you can use <tt>:selected</tt> to specify selected option tags.
      #
      # Examples:
      #   options_for_select(["Free", "Basic", "Advanced", "Super Platinum"], :disabled => "Super Platinum")
      #     <option value="Free">Free</option>\n<option value="Basic">Basic</option>\n<option value="Advanced">Advanced</option>\n<option value="Super Platinum" disabled="disabled">Super Platinum</option>
      #
      #   options_for_select(["Free", "Basic", "Advanced", "Super Platinum"], :disabled => ["Advanced", "Super Platinum"])
      #     <option value="Free">Free</option>\n<option value="Basic">Basic</option>\n<option value="Advanced" disabled="disabled">Advanced</option>\n<option value="Super Platinum" disabled="disabled">Super Platinum</option>
      #
      #   options_for_select(["Free", "Basic", "Advanced", "Super Platinum"], :selected => "Free", :disabled => "Super Platinum")
      #     <option value="Free" selected="selected">Free</option>\n<option value="Basic">Basic</option>\n<option value="Advanced">Advanced</option>\n<option value="Super Platinum" disabled="disabled">Super Platinum</option>
      #
      # NOTE: Only the option tags are returned, you have to wrap this call in a regular HTML select tag.
      def options_for_select(container, selected = nil)
        return container if String === container

        selected, disabled = extract_selected_and_disabled(selected).map do |r|
          Array(r).map { |item| item.to_s }
        end

        container.map do |element|
          html_attributes = option_html_attributes(element)
          text, value = option_text_and_value(element).map { |item| item.to_s }
          selected_attribute = ' selected="selected"' if option_value_selected?(value, selected)
          disabled_attribute = ' disabled="disabled"' if disabled && option_value_selected?(value, disabled)
          %(<option value="#{ERB::Util.html_escape(value)}"#{selected_attribute}#{disabled_attribute}#{html_attributes}>#{ERB::Util.html_escape(text)}</option>)
        end.join("\n").html_safe
      end

      # Returns a string of option tags that have been compiled by iterating over the +collection+ and assigning
      # the result of a call to the +value_method+ as the option value and the +text_method+ as the option text.
      # Example:
      #   options_from_collection_for_select(@people, 'id', 'name')
      # This will output the same HTML as if you did this:
      #   <option value="#{person.id}">#{person.name}</option>
      #
      # This is more often than not used inside a #select_tag like this example:
      #   select_tag 'person', options_from_collection_for_select(@people, 'id', 'name')
      #
      # If +selected+ is specified as a value or array of values, the element(s) returning a match on +value_method+
      # will be selected option tag(s).
      #
      # If +selected+ is specified as a Proc, those members of the collection that return true for the anonymous
      # function are the selected values.
      #
      # +selected+ can also be a hash, specifying both <tt>:selected</tt> and/or <tt>:disabled</tt> values as required.
      #
      # Be sure to specify the same class as the +value_method+ when specifying selected or disabled options.
      # Failure to do this will produce undesired results. Example:
      #   options_from_collection_for_select(@people, 'id', 'name', '1')
      # Will not select a person with the id of 1 because 1 (an Integer) is not the same as '1' (a string)
      #   options_from_collection_for_select(@people, 'id', 'name', 1)
      # should produce the desired results.
      def options_from_collection_for_select(collection, value_method, text_method, selected = nil)
        options = collection.map do |element|
          [value_for_collection(element, text_method), value_for_collection(element, value_method)]
        end
        selected, disabled = extract_selected_and_disabled(selected)
        select_deselect = {
          :selected => extract_values_from_collection(collection, value_method, selected),
          :disabled => extract_values_from_collection(collection, value_method, disabled)
        }

        options_for_select(options, select_deselect)
      end

      # Returns a string of <tt><option></tt> tags, like <tt>options_from_collection_for_select</tt>, but
      # groups them by <tt><optgroup></tt> tags based on the object relationships of the arguments.
      #
      # Parameters:
      # * +collection+ - An array of objects representing the <tt><optgroup></tt> tags.
      # * +group_method+ - The name of a method which, when called on a member of +collection+, returns an
      #   array of child objects representing the <tt><option></tt> tags.
      # * group_label_method+ - The name of a method which, when called on a member of +collection+, returns a
      #   string to be used as the +label+ attribute for its <tt><optgroup></tt> tag.
      # * +option_key_method+ - The name of a method which, when called on a child object of a member of
      #   +collection+, returns a value to be used as the +value+ attribute for its <tt><option></tt> tag.
      # * +option_value_method+ - The name of a method which, when called on a child object of a member of
      #   +collection+, returns a value to be used as the contents of its <tt><option></tt> tag.
      # * +selected_key+ - A value equal to the +value+ attribute for one of the <tt><option></tt> tags,
      #   which will have the +selected+ attribute set. Corresponds to the return value of one of the calls
      #   to +option_key_method+. If +nil+, no selection is made. Can also be a hash if disabled values are
      #   to be specified.
      #
      # Example object structure for use with this method:
      #   class Continent < ActiveRecord::Base
      #     has_many :countries
      #     # attribs: id, name
      #   end
      #   class Country < ActiveRecord::Base
      #     belongs_to :continent
      #     # attribs: id, name, continent_id
      #   end
      #
      # Sample usage:
      #   option_groups_from_collection_for_select(@continents, :countries, :name, :id, :name, 3)
      #
      # Possible output:
      #   <optgroup label="Africa">
      #     <option value="1">Egypt</option>
      #     <option value="4">Rwanda</option>
      #     ...
      #   </optgroup>
      #   <optgroup label="Asia">
      #     <option value="3" selected="selected">China</option>
      #     <option value="12">India</option>
      #     <option value="5">Japan</option>
      #     ...
      #   </optgroup>
      #
      # <b>Note:</b> Only the <tt><optgroup></tt> and <tt><option></tt> tags are returned, so you still have to
      # wrap the output in an appropriate <tt><select></tt> tag.
      def option_groups_from_collection_for_select(collection, group_method, group_label_method, option_key_method, option_value_method, selected_key = nil)
        collection.map do |group|
          option_tags = options_from_collection_for_select(
            group.send(group_method), option_key_method, option_value_method, selected_key)

          content_tag(:optgroup, option_tags, :label => group.send(group_label_method))
        end.join.html_safe
      end

      # Returns a string of <tt><option></tt> tags, like <tt>options_for_select</tt>, but
      # wraps them with <tt><optgroup></tt> tags.
      #
      # Parameters:
      # * +grouped_options+ - Accepts a nested array or hash of strings. The first value serves as the
      #   <tt><optgroup></tt> label while the second value must be an array of options. The second value can be a
      #   nested array of text-value pairs. See <tt>options_for_select</tt> for more info.
      #    Ex. ["North America",[["United States","US"],["Canada","CA"]]]
      # * +selected_key+ - A value equal to the +value+ attribute for one of the <tt><option></tt> tags,
      #   which will have the +selected+ attribute set. Note: It is possible for this value to match multiple options
      #   as you might have the same option in multiple groups. Each will then get <tt>selected="selected"</tt>.
      # * +prompt+ - set to true or a prompt string. When the select element doesn't have a value yet, this
      #   prepends an option with a generic prompt - "Please select" - or the given prompt string.
      #
      # Sample usage (Array):
      #   grouped_options = [
      #    ['North America',
      #      [['United States','US'],'Canada']],
      #    ['Europe',
      #      ['Denmark','Germany','France']]
      #   ]
      #   grouped_options_for_select(grouped_options)
      #
      # Sample usage (Hash):
      #   grouped_options = {
      #    'North America' => [['United States','US'], 'Canada'],
      #    'Europe' => ['Denmark','Germany','France']
      #   }
      #   grouped_options_for_select(grouped_options)
      #
      # Possible output:
      #   <optgroup label="Europe">
      #     <option value="Denmark">Denmark</option>
      #     <option value="Germany">Germany</option>
      #     <option value="France">France</option>
      #   </optgroup>
      #   <optgroup label="North America">
      #     <option value="US">United States</option>
      #     <option value="Canada">Canada</option>
      #   </optgroup>
      #
      # <b>Note:</b> Only the <tt><optgroup></tt> and <tt><option></tt> tags are returned, so you still have to
      # wrap the output in an appropriate <tt><select></tt> tag.
      def grouped_options_for_select(grouped_options, selected_key = nil, prompt = nil)
        body = ''
        body << content_tag(:option, prompt, { :value => "" }, true) if prompt

        grouped_options = grouped_options.sort if grouped_options.is_a?(Hash)

        grouped_options.each do |group|
          body << content_tag(:optgroup, options_for_select(group[1], selected_key), :label => group[0])
        end

        body.html_safe
      end

      # Returns a string of option tags for pretty much any time zone in the
      # world. Supply a ActiveSupport::TimeZone name as +selected+ to have it
      # marked as the selected option tag. You can also supply an array of
      # ActiveSupport::TimeZone objects as +priority_zones+, so that they will
      # be listed above the rest of the (long) list. (You can use
      # ActiveSupport::TimeZone.us_zones as a convenience for obtaining a list
      # of the US time zones, or a Regexp to select the zones of your choice)
      #
      # The +selected+ parameter must be either +nil+, or a string that names
      # a ActiveSupport::TimeZone.
      #
      # By default, +model+ is the ActiveSupport::TimeZone constant (which can
      # be obtained in Active Record as a value object). The only requirement
      # is that the +model+ parameter be an object that responds to +all+, and
      # returns an array of objects that represent time zones.
      #
      # NOTE: Only the option tags are returned, you have to wrap this call in
      # a regular HTML select tag.
      def time_zone_options_for_select(selected = nil, priority_zones = nil, model = ::ActiveSupport::TimeZone)
        zone_options = ""

        zones = model.all
        convert_zones = lambda { |list| list.map { |z| [ z.to_s, z.name ] } }

        if priority_zones
          if priority_zones.is_a?(Regexp)
            priority_zones = model.all.find_all {|z| z =~ priority_zones}
          end
          zone_options += options_for_select(convert_zones[priority_zones], selected)
          zone_options += "<option value=\"\" disabled=\"disabled\">-------------</option>\n"

          zones = zones.reject { |z| priority_zones.include?( z ) }
        end

        zone_options += options_for_select(convert_zones[zones], selected)
        zone_options.html_safe
      end

      # Returns radio button tags for the collection of existing return values
      # of +method+ for +object+'s class. The value returned from calling
      # +method+ on the instance +object+ will be selected. If calling +method+
      # returns +nil+, no selection is made.
      #
      # The <tt>:value_method</tt> and <tt>:text_method</tt> parameters are
      # methods to be called on each member of +collection+. The return values
      # are used as the +value+ attribute and contents of each radio button tag,
      # respectively. They can also be any object that responds to +call+, such
      # as a +proc+, that will be called for each member of the +collection+ to
      # retrieve the value/text.
      #
      # Example object structure for use with this method:
      #   class Post < ActiveRecord::Base
      #     belongs_to :author
      #   end
      #   class Author < ActiveRecord::Base
      #     has_many :posts
      #     def name_with_initial
      #       "#{first_name.first}. #{last_name}"
      #     end
      #   end
      #
      # Sample usage (selecting the associated Author for an instance of Post, <tt>@post</tt>):
      #   collection_radio_buttons(:post, :author_id, Author.all, :id, :name_with_initial)
      #
      # If <tt>@post.author_id</tt> is already <tt>1</tt>, this would return:
      #   <input id="post_author_id_1" name="post[author_id]" type="radio" value="1" checked="checked" />
      #   <label class="collection_radio_buttons" for="post_author_id_1">D. Heinemeier Hansson</label>
      #   <input id="post_author_id_2" name="post[author_id]" type="radio" value="2" />
      #   <label class="collection_radio_buttons" for="post_author_id_2">D. Thomas</label>
      #   <input id="post_author_id_3" name="post[author_id]" type="radio" value="3" />
      #   <label class="collection_radio_buttons" for="post_author_id_3">M. Clark</label>
      #
      # It is also possible to customize the way the elements will be shown by
      # giving a block to the method:
      #   collection_radio_buttons(:post, :author_id, Author.all, :id, :name_with_initial) do |b|
      #     b.label { b.radio_button }
      #   end
      #
      # The argument passed to the block is a special kind of builder for this
      # collection, which has the ability to generate the label and radio button
      # for the current item in the collection, with proper text and value.
      # Using it, you can change the label and radio button display order or
      # even use the label as wrapper, as in the example above.
      #
      # The builder methods <tt>label</tt> and <tt>radio_button</tt> also accept
      # extra html options:
      #   collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial) do |b|
      #     b.label(:class => "radio_button") { b.radio_button(:class => "radio_button") }
      #   end
      def collection_radio_buttons(object, method, collection, value_method, text_method, options = {}, html_options = {}, &block)
        Tags::CollectionRadioButtons.new(object, method, self, collection, value_method, text_method, options, html_options).render(&block)
      end

      # Returns check box tags for the collection of existing return values of
      # +method+ for +object+'s class. The value returned from calling +method+
      # on the instance +object+ will be selected. If calling +method+ returns
      # +nil+, no selection is made.
      #
      # The <tt>:value_method</tt> and <tt>:text_method</tt> parameters are
      # methods to be called on each member of +collection+. The return values
      # are used as the +value+ attribute and contents of each check box tag,
      # respectively. They can also be any object that responds to +call+, such
      # as a +proc+, that will be called for each member of the +collection+ to
      # retrieve the value/text.
      #
      # Example object structure for use with this method:
      #   class Post < ActiveRecord::Base
      #     has_and_belongs_to_many :author
      #   end
      #   class Author < ActiveRecord::Base
      #     has_and_belongs_to_many :posts
      #     def name_with_initial
      #       "#{first_name.first}. #{last_name}"
      #     end
      #   end
      #
      # Sample usage (selecting the associated Author for an instance of Post, <tt>@post</tt>):
      #   collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial)
      #
      # If <tt>@post.author_ids</tt> is already <tt>[1]</tt>, this would return:
      #   <input id="post_author_ids_1" name="post[author_ids][]" type="checkbox" value="1" checked="checked" />
      #   <label class="collection_check_boxes" for="post_author_ids_1">D. Heinemeier Hansson</label>
      #   <input id="post_author_ids_2" name="post[author_ids][]" type="checkbox" value="2" />
      #   <label class="collection_check_boxes" for="post_author_ids_2">D. Thomas</label>
      #   <input id="post_author_ids_3" name="post[author_ids][]" type="checkbox" value="3" />
      #   <label class="collection_check_boxes" for="post_author_ids_3">M. Clark</label>
      #   <input name="post[author_ids][]" type="hidden" value="" />
      #
      # It is also possible to customize the way the elements will be shown by
      # giving a block to the method:
      #   collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial) do |b|
      #     b.label { b.check_box }
      #   end
      #
      # The argument passed to the block is a special kind of builder for this
      # collection, which has the ability to generate the label and check box
      # for the current item in the collection, with proper text and value.
      # Using it, you can change the label and check box display order or even
      # use the label as wrapper, as in the example above.
      #
      # The builder methods <tt>label</tt> and <tt>check_box</tt> also accept
      # extra html options:
      #   collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial) do |b|
      #     b.label(:class => "check_box") { b.check_box(:class => "check_box") }
      #   end
      def collection_check_boxes(object, method, collection, value_method, text_method, options = {}, html_options = {}, &block)
        Tags::CollectionCheckBoxes.new(object, method, self, collection, value_method, text_method, options, html_options).render(&block)
      end

      private
        def option_html_attributes(element)
          return "" unless Array === element

          element.select { |e| Hash === e }.reduce({}, :merge).map do |k, v|
            " #{k}=\"#{ERB::Util.html_escape(v.to_s)}\""
          end.join
        end

        def option_text_and_value(option)
          # Options are [text, value] pairs or strings used for both.
          case
          when Array === option
            option = option.reject { |e| Hash === e }
            [option.first, option.last]
          when !option.is_a?(String) && option.respond_to?(:first) && option.respond_to?(:last)
            [option.first, option.last]
          else
            [option, option]
          end
        end

        def option_value_selected?(value, selected)
          if selected.respond_to?(:include?) && !selected.is_a?(String)
            selected.include? value
          else
            value == selected
          end
        end

        def extract_selected_and_disabled(selected)
          if selected.is_a?(Proc)
            [selected, nil]
          else
            selected = Array.wrap(selected)
            options = selected.extract_options!.symbolize_keys
            selected_items = options.fetch(:selected, selected)
            [selected_items, options[:disabled]]
          end
        end

        def extract_values_from_collection(collection, value_method, selected)
          if selected.is_a?(Proc)
            collection.map do |element|
              element.send(value_method) if selected.call(element)
            end.compact
          else
            selected
          end
        end

        def value_for_collection(item, value)
          value.respond_to?(:call) ? value.call(item) : item.send(value)
        end
    end

    class FormBuilder
      def select(method, choices, options = {}, html_options = {})
        @template.select(@object_name, method, choices, objectify_options(options), @default_options.merge(html_options))
      end

      def collection_select(method, collection, value_method, text_method, options = {}, html_options = {})
        @template.collection_select(@object_name, method, collection, value_method, text_method, objectify_options(options), @default_options.merge(html_options))
      end

      def grouped_collection_select(method, collection, group_method, group_label_method, option_key_method, option_value_method, options = {}, html_options = {})
        @template.grouped_collection_select(@object_name, method, collection, group_method, group_label_method, option_key_method, option_value_method, objectify_options(options), @default_options.merge(html_options))
      end

      def time_zone_select(method, priority_zones = nil, options = {}, html_options = {})
        @template.time_zone_select(@object_name, method, priority_zones, objectify_options(options), @default_options.merge(html_options))
      end

      def collection_check_boxes(method, collection, value_method, text_method, options = {}, html_options = {})
        @template.collection_check_boxes(@object_name, method, collection, value_method, text_method, objectify_options(options), @default_options.merge(html_options))
      end

      def collection_radio_buttons(method, collection, value_method, text_method, options = {}, html_options = {})
        @template.collection_radio_buttons(@object_name, method, collection, value_method, text_method, objectify_options(options), @default_options.merge(html_options))
      end
    end
  end
end