Passing an array into hidden_field ROR - ruby-on-rails

Question

I'm trying to pass an array into a hidden_field.
The following User has 3 roles [2,4,5]
>> u = User.find_by_login("lesa")
=> #<User id: 5, login: "lesa", email: "lesa.beaupry#gmail.com", crypted_password: "0f2776e68f1054a2678ad69a3b28e35ad9f42078", salt: "f02ef9e00d16f1b9f82dfcc488fdf96bf5aab4a8", created_at: "2009-12-29 15:15:51", updated_at: "2010-01-06 06:27:16", remember_token: nil, remember_token_expires_at: nil>
>> u.roles.map(&:id)
=> [2, 4, 5]
Users/edit.html.erb
<% form_for #user do |f| -%>
<%= f.hidden_field :role_ids, :value => #user.roles.map(&:id) %>
When I submit my edit form, I receive an error: ActiveRecord::RecordNotFound in UsersController#update "Couldn't find Role with ID=245"
How can I pass an array into the hidden_field?

Answer 1

I would use this technique.
<% #user.roles.each do |role| %>
<%= f.hidden_field :role_ids, :multiple => true, :value => role.id %>
<% end %>
:multiple adds both the [] to the end of the name attribute and multiple="multiple" to the input element, which is ideal. Rails uses this internally when it generates inputs for arrays, such as in fields_for.
Unfortunately it is not well-documented. I'm going to look into fixing this.

Answer 2

The only thing that works for me (Rails 3.1) is using hidden_field_tag:
<% #users.roles.each do |role| %>
<%= hidden_field_tag "user_role_ids[]", role.id %>
<% end %>

Answer 3

Try:
<% #user.roles.each_with_index do |role| %>
<%= f.hidden_field "role_ids[]", :value => role.id %>
<% end %>

Answer 4

using Rails 4.2.6
I was able to use
<% #user.roles.each do |role|
<%= f.hidden_field :role_ids, :id => role.id, :value => role.id, :multiple => true %>
<% end %>
which rendered:
<input id="12345" value="12345" multiple="multiple" type="hidden" name="role_form[role_ids][]">
trying to use hidden_field_tag or the 'role_ids[]' the param details were not being included in my form_params.
This didn't work:
<% #user.roles.each do |role|
<%= hidden_field_tag 'role_ids[]', role %>
<% end %>
because it renders:
<input type="hidden" name="role_ids[]" id="role_ids_" value="12345">
and is seen by the controller outside of the form params.

Answer 5

try with:
<%= f.hidden_field :role_ids, :value => #user.roles.map(&:id).join(", ") %>
edit: note - you'll need to do ids.split(", ") in your controller to convert them from a string into an array

Answer 6

I realize the original question involved a Rails form_for form, but I just encountered this problem while trying adding a hidden field to a form_tag form. The solution is slightly different.
The hidden_field_tag kept converting my ids to a space-separated string, like "1 2 3", not the array of ["1", "2", "3"] that I wanted. According to the docs, this is a known problem with hidden_field_tag. This is the approach that ended up working for my Rails 6 form_tag form:
In the view:
<%= hidden_field_tag :role_ids, my_role_ids_array %>
In the controller:
role_ids = params[:role_ids].split(' ').map(&:to_i)

Answer 7

Could solve this kind of issue with :
<% params[:filter].each do |filter| %>
<%= hidden_field_tag 'filter[]', filter %>
<% end %>