app/views/proposition/units/_form.html.erb
<%= simple_form_for(@unit, html: { class: 'form-horizontal' }, wrapper: :horizontal_form) do |f| %>
<%= render partial: 'shared/form/error_messages', locals: { resource: @unit } %>
<%= f.hidden_field :parent_id %>
<%= f.input :organization_id, collection: current_user.organizations %>
<%= f.input :name %>
<div class="form-group">
<div class="col-sm-offset-3 col-sm-9">
<%= f.button :submit %>
</div>
</div>
<% end %>