app/views/mypage/_user_form.html.erb
<%= form_tag("/tktl-labtool/mypage/#{@user.student_number}", :method => :put) do -%>
<div class="field">
<%= label_tag 'forename' %>
<br/>
<%= text_field_tag 'user[forename]', @user.forename %>
</div>
<div class="field">
<%= label_tag 'surename' %>
<br/>
<%= text_field_tag 'user[surename]', @user.surename %>
</div>
<div class="field">
<%= label_tag 'email' %>
<br/>
<%= text_field_tag 'user[email]', @user.email %>
</div>
<% if @user.current_registration %>
<div class="field">
<%= label_tag 'topic' %>
<br/>
<%= text_field_tag 'user[registration][topic]', @user.current_registration.topic %>
</div>
<div class="field">
<%= label_tag 'github repository' %>
<br/>
<%= text_field_tag 'user[registration][repository]', @user.current_registration.repository %>
</div>
<% end %>
<%= submit_tag "Make changes" %>
<% end -%>