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 :value_method and :text_method 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 :authors
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, @post):

collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial)

If @post.author_ids is already [1], this would return:

<input id="post_author_ids_1" name="post[author_ids][]" type="checkbox" value="1" checked="checked" />
<label for="post_author_ids_1">D. Heinemeier Hansson</label>
<input id="post_author_ids_2" name="post[author_ids][]" type="checkbox" value="2" />
<label for="post_author_ids_2">D. Thomas</label>
<input id="post_author_ids_3" name="post[author_ids][]" type="checkbox" value="3" />
<label 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 label and check_box 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

There are also three special methods available: object, text and value, which are the current item being rendered, its text and value methods, respectively. You can use them like this:

collection_check_boxes(:post, :author_ids, Author.all, :id, :name_with_initial) do |b|
   b.label(:"data-value" => b.value) { b.check_box + b.text }
end

Gotcha

When no selection is made for a collection of checkboxes most web browsers will not send any value.

For example, if we have a User model with category_ids field and we have the following code in our update action:

@user.update(params[:user])

If no category_ids are selected then we can safely assume this field will not be updated.

This is possible thanks to a hidden field generated by the helper method for every collection of checkboxes. This hidden field is given the same field name as the checkboxes with a blank value.

In the rare case you don't want this hidden field, you can pass the include_hidden: false option to the helper method.

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 :value_method and :text_method 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, @post):

collection_radio_buttons(:post, :author_id, Author.all, :id, :name_with_initial)

If @post.author_id is already 1, this would return:

<input id="post_author_id_1" name="post[author_id]" type="radio" value="1" checked="checked" />
<label for="post_author_id_1">D. Heinemeier Hansson</label>
<input id="post_author_id_2" name="post[author_id]" type="radio" value="2" />
<label for="post_author_id_2">D. Thomas</label>
<input id="post_author_id_3" name="post[author_id]" type="radio" value="3" />
<label 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 label and radio_button also accept extra HTML options:

collection_radio_buttons(:post, :author_id, Author.all, :id, :name_with_initial) do |b|
  b.label(class: "radio_button") { b.radio_button(class: "radio_button") }
end

There are also three special methods available: object, text and value, which are the current item being rendered, its text and value methods, respectively. You can use them like this:

collection_radio_buttons(:post, :author_id, Author.all, :id, :name_with_initial) do |b|
   b.label(:"data-value" => b.value) { b.radio_button + b.text }
end

Gotcha

The HTML specification says when nothing is select on a collection of radio buttons web browsers do not send any value to server. Unfortunately this introduces a gotcha: if a User model has a category_id field and in the form no category is selected, no category_id parameter is sent. So, any strong parameters idiom like:

params.require(:user).permit(...)

will raise an error since no {user: ...} will be present.

To prevent this the helper generates an auxiliary hidden field before every collection of radio buttons. The hidden field has the same name as collection radio button and blank value.

In case if you don't want the helper to generate this hidden field you can specify include_hidden: false option.

Returns <select> and <option> 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 :prompt or :include_blank in the options hash.

The :value_method and :text_method parameters are methods to be called on each member of collection. The return values are used as the value attribute and contents of each <option> 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, @post):

collection_select(:post, :author_id, Author.all, :id, :name_with_initial, prompt: true)

If @post.author_id is already 1, this would return:

<select name="post[author_id]" id="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>

Returns <select>, <optgroup> and <option> 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 :prompt or :include_blank 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 <optgroup> tags.

• group_method - The name of a method which, when called on a member of collection, returns an array of child objects representing the <option> 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 <optgroup> 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 <option> 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 <option> 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]" id="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>

Returns a string of <option> tags, like options_for_select, but wraps them with <optgroup> tags:

grouped_options = [
 ['North America',
   [['United States','US'],'Canada']],
 ['Europe',
   ['Denmark','Germany','France']]
]
grouped_options_for_select(grouped_options)

grouped_options = {
  'North America' => [['United States','US'], 'Canada'],
  'Europe' => ['Denmark','Germany','France']
}
grouped_options_for_select(grouped_options)

Possible output:

<optgroup label="North America">
  <option value="US">United States</option>
  <option value="Canada">Canada</option>
</optgroup>
<optgroup label="Europe">
  <option value="Denmark">Denmark</option>
  <option value="Germany">Germany</option>
  <option value="France">France</option>
</optgroup>

Parameters:

• grouped_options - Accepts a nested array or hash of strings. The first value serves as the <optgroup> label while the second value must be an array of options. The second value can be a nested array of text-value pairs. See options_for_select for more info.

  Ex. ["North America",[["United States","US"],["Canada","CA"]]]

• selected_key - A value equal to the value attribute for one of the <option> 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 selected="selected".

Options:

• :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.

• :divider - the divider for the options groups.

  grouped_options = [
    [['United States','US'], 'Canada'],
    ['Denmark','Germany','France']
  ]
  grouped_options_for_select(grouped_options, nil, divider: '---------')
  

  Possible output:

  <optgroup label="---------">
    <option value="US">United States</option>
    <option value="Canada">Canada</option>
  </optgroup>
  <optgroup label="---------">
    <option value="Denmark">Denmark</option>
    <option value="Germany">Germany</option>
    <option value="France">France</option>
  </optgroup>

Note: Only the <optgroup> and <option> tags are returned, so you still have to wrap the output in an appropriate <select> tag.

Returns a string of <option> tags, like options_from_collection_for_select, but groups them by <optgroup> tags based on the object relationships of the arguments.

Parameters:

• collection - An array of objects representing the <optgroup> tags.

• group_method - The name of a method which, when called on a member of collection, returns an array of child objects representing the <option> 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 <optgroup> 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 <option> 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 <option> tag.

• selected_key - A value equal to the value attribute for one of the <option> 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>

Note: Only the <optgroup> and <option> tags are returned, so you still have to wrap the output in an appropriate <select> tag.

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.

options_for_select([["Dollar", "$"], ["Kroner", "DKK"]])
# => <option value="$">Dollar</option>
# => <option value="DKK">Kroner</option>

options_for_select([ "VISA", "MasterCard" ], "MasterCard")
# => <option value="VISA">VISA</option>
# => <option selected="selected" value="MasterCard">MasterCard</option>

options_for_select({ "Basic" => "$20", "Plus" => "$40" }, "$40")
# => <option value="$20">Basic</option>
# => <option value="$40" selected="selected">Plus</option>

options_for_select([ "VISA", "MasterCard", "Discover" ], ["VISA", "Discover"])
# => <option selected="selected" value="VISA">VISA</option>
# => <option value="MasterCard">MasterCard</option>
# => <option selected="selected" value="Discover">Discover</option>

You can optionally provide HTML attributes as the last element of the array.

options_for_select([ "Denmark", ["USA", {class: 'bold'}], "Sweden" ], ["USA", "Sweden"])
# => <option value="Denmark">Denmark</option>
# => <option value="USA" class="bold" selected="selected">USA</option>
# => <option value="Sweden" selected="selected">Sweden</option>

options_for_select([["Dollar", "$", {class: "bold"}], ["Kroner", "DKK", {onclick: "alert('HI');"}]])
# => <option value="$" class="bold">Dollar</option>
# => <option value="DKK" onclick="alert('HI');">Kroner</option>

If you wish to specify disabled option tags, set selected to be a hash, with :disabled being either a value or array of values to be disabled. In this case, you can use :selected to specify selected option tags.

options_for_select(["Free", "Basic", "Advanced", "Super Platinum"], disabled: "Super Platinum")
# => <option value="Free">Free</option>
# => <option value="Basic">Basic</option>
# => <option value="Advanced">Advanced</option>
# => <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>
# => <option value="Basic">Basic</option>
# => <option value="Advanced" disabled="disabled">Advanced</option>
# => <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>
# => <option value="Basic">Basic</option>
# => <option value="Advanced">Advanced</option>
# => <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.

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.

options_from_collection_for_select(@people, 'id', 'name')
# => <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 :selected and/or :disabled 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.

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).

For example:

select("post", "person_id", Person.all.collect {|p| [ p.name, p.id ] }, { include_blank: true })

would become:

<select name="post[person_id]" id="post_person_id">
  <option value=""></option>
  <option value="1" selected="selected">David</option>
  <option value="2">Eileen</option>
  <option value="3">Rafael</option>
</select>

assuming the associated person has ID 1.

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, post.person_id is the selected option. Specify selected: value to use a different selection or selected: nil to leave all options unselected. Similarly, you can specify values to be disabled in the option tags by specifying the :disabled option. This can either be a single value or an array of values to be disabled.

A block can be passed to select to customize how the options tags will be rendered. This is useful when the options tag has complex attributes.

select(report, "campaign_ids") do
  available_campaigns.each do |c|
    content_tag(:option, c.name, value: c.id, data: { tags: c.tags.to_json })
  end
end

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(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.

Note: The client either sends only the hidden field (representing the deselected multiple select box), or both fields. This means that the resulting array always contains a blank string.

In case if you don't want the helper to generate this hidden field you can specify include_hidden: false option.

Returns a string of option tags for pretty much any time zone in the world. Supply an 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 an 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.

Returns 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 :include_blank option documented above, this method also supports a :model 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 for a list of US time zones, ActiveSupport::TimeZone.country_zones for another country's time zones, or a Regexp to select the zones of your choice.

Finally, this method supports a :default option, which selects a default ActiveSupport::TimeZone if the object's time zone is nil.

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)