<%= f.label a.keys.first, class: "form-control-label #{required?(f.object, a).present? ? 'required' : ''}" %>

<%= f.hidden_field a.keys.first, class: 'form-control', id: f.options[:html][:id] + '_' + a.keys.first.to_s, required: required?(f.object, a), value: f.object.send(a.keys.first.to_s).to_json %>