= simple_form_for(@images_activity) do |f|
  = f.error_notification

  .form-inputs
    - if params[:activity]
      - param = params[:activity]
    - else
      - param = @images_activity.activity_id
    = f.input :activity_id, as: :hidden, input_html: { value: param }
    = f.input :position, as: :hidden, input_html: { value: @activity_position }
    = f.input :image

  .form-actions
    = f.button :submit