ボタンによって処理を切り替える

submit_tagの場合
view

<% form_tag -%>
  <%= submit_tag("Search", :name => "search") %>
  <%= submit_tag("Delete", :name => "delete") %>
<% end -%>

controller

if params[:search]
  // ...
elsif params[:delete]
  // ...
end

image_submit_tagの場合
view

<% form_tag -%>
  <%= image_submit_tag("search.png", :name => "search") %>
  <%= image_submit_tag("delete.png", :name => "delete") %>
<% end -%>

controller

if params['search.x']
  // ...
elsif params['delete.x']
  // ...
end