modal.erb

bootstrap_modal(dom_id: 'a_dom_id', fade: true, header_title: "I'm a bootstrap modal popup") do |modal|
  modal.body do |c|
   c.content_tag :div, "the body"
  end
  modal.footer do |f|
    f.bootstrap_button "Save", "/link1", :type => 'btn-primary'
    f.bootstrap_button "Cancel", "/link2"
  end
end

modal.slim

#a_dom_id.modal.fade
  .modal-header
    a.close data-dismiss="modal" &times
    h3 I'm a bootstrap modal popup
  .modal-body
    div the body
  .modal-footer
    a.btn.btn-primary href='/link1' Save
    a.btn href='/link2' Cancel