Edit form problem

I have this form
<%= form_for @lesson do |f| %>
          <%= f.label :lesson_name, "Lesson title" %></br>
          <%= f.text_field :lesson_name, class: "form-control" %></br>
          <%= f.label :lesson_icon, "Choise icon" %>
          <%= f.select "lesson_icon", options_for_select([ "ico-03",
"ico-04","ico-05","ico-06" ])%></br></br>
            <p style="display:none"><%=hh=0%></p>
           <%= f.fields_for :sublessons do |sublesson_a| %>

           <div class="delete-subtitle-<%=hh%>" style="padding-bottom:
              <%= sublesson_a.label :sublesson_name, "Subtitle 1"
              <%= sublesson_a.text_field :sublesson_name, class:
"form-control delete-sublesson-field-#{hh}" %></br>
              <%= sublesson_a.label :sublesson_content, "Content"
              <%=sublesson_a.text_area 'sublesson_content', rows: 3,
class: "form-control delete-sublesson-content-#{hh}"%></br>
              <%= sublesson_a.label :sublesson_video_link, "Video link"
              <%= sublesson_a.text_field :sublesson_video_link, class:
"form-control delete-sublesson-video-#{hh}" %></br>
              <a style="float:right" class="btn btn-primary"
id="remove_sublesson" onclick="remove_sublesson(<%=hh%>)">Delete
              <p style="display:none"><%= hh=hh+1%></p>


        <%= f.submit "Submit", class: "btn btn-primary" %>
        <a class="btn btn-primary" id="addNewTag"
onclick="add_sublesson()">Add Sublesson</a>

      <% end %>

This is a form for edit....How can i test if :sublessons is empty?

I suppose that your lesson ‘has_many’ sublessons. In this case you can check it as follows:

if @lesson.sublessons.any?

It returns true if the collection is not empty