Updating shopping cart

You want to update a cart count located in the header when a user clicks on "Add to cart" on a product listing.

  <form action='/add_to_cart?bzq=data.header.cart' method='POST' data-bz-remote={true}>

def create
  ... add to cart logic here...

  # This helper will retain the `bzq` param when redirecting, which allows the
  # partial rendering of the `show` page.
  redirect_back_with_bzq fallback_url: '/'
end

The above will POST, and get redirected back to the original page while fetching only the header to update.