Agile Web Development with Rails 7: Getting or creating a cart (page 114) (solved)

Hi all,

the code on page 117 to get the of create a cart object is:

def set_cart
  @cart = Cart.find(session[:cart_id])
rescue ActiveRecord::RecordNotFound 
  @cart = Cart.create 
  session[:cart_id] = @cart.id
end

Since I’d expect to not find a cart, I think it’s not very exceptional to not find a cart.
Therefore, I would probably tend to not using an exception to control the program flow and use code like this instead:

def set_cart
  @cart = Cart.find_by(id: session[:cart_id])
  return unless @cart.nil?

  @cart = Cart.new
  session[:cart_id] = @cart.id
end

Or maybe this:

def set_cart
  @cart = Cart.find_by(id: session[:cart_id])
  if @cart.nil?
    @cart = Cart.new
    session[:cart_id] = @cart.id
  end
end

I must say that I also do like the

def …
  # …
rescue … 
  # … 
end

notation (a lot), provided that the rescued behaviour is in fact exceptional.
Am I wrong? What are other people thinking about this?