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> 

• :index - 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>