<%= simple_form_for :product, method: :put  do |f| %>
<%= f.input :product_id, :collection => @allProducts,  :value_method => :id,:label => "Products" ,:include_blank => true %>
<%= f.input :quantity %>

<%= f.button :submit, 'Add to Stock', class: 'btn btn-success add-sale-item' %>