Flowdock
select(object, method, choices, options = {}, html_options = {}) public

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, 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.

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.

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July 22, 2008
15 thanks

Demo: select onchange invoke an ajax

select(“order”, “customer_id”, o.customer.collect {|c| [ c.label, c.id ] },

{:include_blank => true, :selected => o.customer_id }, 
:onchange => remote_function(:update => "message_id",
:method => "put",
:with => "'item=' + value",  
:url => { :controller => :orders, :action => :set_customer_id, :id => order.id}))
July 4, 2008
12 thanks

Add empty option and text is -select-

select :object, :method, options, :prompt => ‘-select-’

October 24, 2008
11 thanks

Prompt vs. Select

According to the docs in form_options_helper.rb

: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.

: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.

The main difference is that if the select already has a value, then :prompt will not show whereas the :include_blank always will.

January 8, 2009
10 thanks

Refactoring excessive code for selects

@garg: It is not recommended to have excessive code in the views. You should refactor your code a bit.

<%= f.select(:manufacturer_id, Manufacturer.find(:all).collect {|u| [u.name, u.id]}, :prompt => 'Select') %>

could be changed to this:

# in app/helpers/manufacturer_helper.rb
def manufacturers_for_select
  Manufacturer.all.collect { |m| [m.name, m.id] }
end

# in the view
<%= f.select(:manufacturer_id, manufacturers_for_select, :prompt => 'Select') %>

I would look into collection_select though:

<%= f.collection_select(:manufacturer_id, Manufacturer.all, :id, :name, :prompt => 'Select') %>

It’s much more clean and you don’t have to define a helper for it to be readable (altough it’s still quite long).

If you have to do this often, you should define a FormBuilder extension, so you get methods like f.manufacturer_select:

<%= f.manufacturer_select(:manufacturer_id, Manufacturer.all) %>

IMO, most projects should have a custom form builder anyway, so the addition would be very small. This is my personal opinion, so you don’t have to listen to it. :-)

July 22, 2008
6 thanks

selected

select :languages, :language, [‘en’, ‘de’, ‘fr’], {:selected=> ‘en’}

July 28, 2008
2 thanks

":prompt" doesn't work

This does not work:

select :object, :method, options, :prompt =>-select-’

This does work:

select :object, :method, {:include_blank =>-select-’}
August 9, 2010
2 thanks

When using enumerables

When using enumerables and storing them as strings in the database don’t forget to use .to_s or the select helper won’t automatically select your choice when viewing your data after save.

Exemple:

dates = 1900..Date.today.year
f.select(:year, dates.collect {|d| [d.to_s,d.to_s]}, {:include_blank => "Select"}, {:class => "some_class"} )
November 13, 2009
1 thank

style for select

<%= select(“post”, “person_id”, Person.all.collect {|p| [ p.name, p.id ] }, {}, :style => “width:100px” %>

August 18, 2009
0 thanks

Using custom object via :object

Sometimes you need use select not only with @object as by default. For example if you have helper method like :

def select_parent_for(page)
  select(:page, :parent_id, Page.all.collect{|p| [p.name, p.id]} ) # <--- mistake!
end

In selected line you will use @page instead parameter of method page.

The options has parameter :object (and all form helpers has such parameter)

Solution:

def select_parent_for(page)
  select(:page, :parent_id, ..., :object => page)
end
December 18, 2008 - (v2.0.0 - v2.2.1)
0 thanks

Belongs_to, Has_many association

I have a belongs_to, has_many association between manufacturer and modelname. (manufacturer has many modelnames).

In the new modelname page, I have a drop down menu that lists all the manufacturers, so I choose eg Dell, and then in modelname.name field I enter inspiron or what ever. To create that drop down I used:

<%= f.select(:manufacturer_id, Manufacturer.find(:all).collect {|u| [u.name, u.id]}, :prompt => 'Select') %>

The reason that works was explained by fcheung and rsl on #rubyonrails. Thanks:

the form builder basically calls the method whose docs you have read, inserting the appropriate first argument

The object is referenced internally when you call f.whatever. in any of those tags, the object is omitted when used on a form block variable

September 22, 2008
0 thanks

Different Options

The docs don’t give any detail to what options are available, so I dug around and I think the only to options are :prompt and :include_blank

October 3, 2011
0 thanks

@Mange

If you’re actually looking to cut down on code why not use .map instead of the longer .collect?

March 27, 2014
0 thanks

Update for Rails 4

In the example

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

It can be updated to

select("post", "person_id", Person.pluck(:name, :id), { include_blank: true })
April 14, 2014 - (v3.2.13)
0 thanks