Rails undefined method 'model_name' for nil:nilClass with nested attributes - ruby-on-rails

Question

I have in my orders/edit.html.erb a form that begins like this:
<%= simple_form_for [#reservation, #order] do |f| %>
Orders Controller:
def edit
#reservation = Reservation.find_by_id(params[:reservation_id])
#order = Order.find_by_id(params[:id])
end
Association:
Reservation :has_one Order
Routes:
resources :reservations do
resources :orders
end
If my path resembles something like /reservations/10/orders/10/edit I end up getting an error from Rails saying NoMethodError in Orders#edit and undefined method 'model_name' for nil:NilClass
When I create a new order the form works perfectly fine so not sure why i'm getting an error all of a sudden, can someone help me with this issue?

Answer 1

Current implementation is prone to failure when the URL supplied either a reservation ID or an order ID that is not valid. Two ways to handle this:
First, let Rails do it for you:
def edit
#reservation = Reservation.find(params[:reservation_id])
#order = Order.find(params[:id])
end
This will raise an ActiveRecord::RecordNotFound error, which, in production, should lead users to your 404 page.
If you'd prefer to keep find_by_id and handle this manually, or to rescue from this error in a different way, you can do:
def edit
#reservation = Reservation.find_by_id(params[:reservation_id])
#order = Order.find_by_id(params[:id])
if #reservation.nil? || #order.nil?
raise ActiveRecord::RecordNotFound.new # Or, do something else
end
end
That would yield the same result as above ... just more code.