ActionView::Helpers::FormOptionsHelper

Provides a number of methods for turning different kinds of containers into a set of option tags.

The collection_select, select and time_zone_select methods take an options parameter, a hash:

• :include_blank - 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.

  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 a belongs_to-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>

• :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.

  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 :index 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.

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>

• :disabled - can be a single value or an array of values that will be disabled options in the final output.

  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 collection_select helper, :disabled can also be a Proc that identifies those options that should be disabled.

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 archived? 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>

actionpack/lib/action_view/helpers/form_options_helper.rb