HTML5 Datalist using Ruby on Rails form_for

_form.html.erb

<%= form_for @person do |f| %>
  <%= f.label :first_name, "First Name" %>:
  <%= f.text_field :first_name, list: 'first-name' %>
  <datalist id="first-name">
    <% Person.all.each do |person| %>
      <option value="<%= person.first_name %>"></option>
    <% end %>
  </datalist>
  <%= f.submit %>
<% end %>

You may also want to do distinct:

<% Person.select(:first_name).distinct.each do |person| %>

datalist#first-name
= options_for_select(Person.pluck(:first_name).uniq, @person.first_name)