_search_form.html.erb

<div class="col-sm-12">
  <%= form_tag(send("#{branch}_posts_path"), 
               :method => "get", 
               id: "search-form") do %>
    <i class="fa fa-search" aria-hidden="true"></i>
    <%= text_field_tag  :search, 
                        params[:search], 
                        placeholder: search_placeholder, 
                        class: "form-control" %>
    <%= render category_field_partial_path %>
  <% end %>
</div><!-- col-sm-12 -->