app/views/page/_add.html.erb
<%- if params[:mode] == 'add' -%>
<%= radio_button_tag 'mode', 'show' -%> <%= t('page.show') -%>
<%= radio_button_tag 'mode', 'add', :checked => true -%> <%= t('page.add') -%>
<%- else -%>
<%= radio_button_tag 'mode', 'show', :checked => true -%> <%= t('page.show') -%>
<%= radio_button_tag 'mode', 'add' -%> <%= t('page.add') -%>
<%- end -%>