Passing an array into hidden_field ROR

arrays, hidden-field, ruby-on-rails

Solution

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.

Problem

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?

Original source