Rails中BookingsController#create获取hotel_id失败报错求助

Let's resolve this issue step by step — the core problem is that your create action isn't receiving the hotel_id parameter, so Rails can't locate the associated Hotel. Here's how to fix it properly:

1. Ensure Proper Nested Routing #

First, make sure your bookings routes are nested under hotels in config/routes.rb. This ensures the hotel_id is included in the URL when accessing booking actions:

resources :hotels do
  resources :bookings, only: [:new, :create] # Add other actions like :show if needed
end

This generates URLs like /hotels/:hotel_id/bookings/new (for the form) and /hotels/:hotel_id/bookings (for the POST request), which will automatically pass hotel_id in params.

2. Update the new Action to Build Associated Booking #

Modify your new action to build the booking directly from the hotel object. This establishes the association upfront, so the form will automatically include the hotel_id when submitted:

def new
  @hotel = Hotel.find(params[:hotel_id])
  @booking = @hotel.bookings.new # This links the booking to the hotel immediately
  
  # Simplify room queries (no need for joins since we already have @hotel)
  room = @hotel.room # Use @hotel.rooms if Hotel has many Rooms
  @single = room.pluck(:single_bedroom_num)
  @double = room.pluck(:double_bedroom_num)
  @suite = room.pluck(:suite_room_num)
  @dormitory = room.pluck(:dormitory_room_num)
  
  # Remove the s/d/su/dor variables — they won't exist in the GET request for new
end

3. Fix the Form to Submit hotel_id #

In your app/views/bookings/new.html.erb form, use the nested model syntax to ensure the hotel_id is included in the form data:

<%= form_with(model: [@hotel, @booking], local: true) do |form| %>
  # Your existing form fields (guest name, dates, room counts, etc.)
  
  # Optional: If you want to explicitly add a hidden field (though the nested model should handle this)
  <%= form.hidden_field :hotel_id, value: @hotel.id %>
  
  <%= form.submit "Book Now" %>
<% end %>

4. Update the create Action to Use the Association #

Modify the create action to use the hotel's booking association, which automatically sets the hotel_id without relying on it being in the submitted params:

def create
  @hotel = Hotel.find(params[:hotel_id])
  @booking = @hotel.bookings.new(book_params) # Association sets hotel_id automatically
  
  if @booking.save
    flash[:notice] = "Booked successfully!" # Use flash[:notice] for redirects (flash.now is for renders)
    redirect_to root_path
  else
    flash.now[:alert] = "Oops, couldn't book."
    render :new
  end
end

5. Verify Strong Parameters #

Your existing book_params already permits :hotel_id, which is fine — but since we're using the association to set it, you don't strictly need it in the permitted list. You can keep it or remove it; either way will work.

Why This Works #

• Nested routes ensure hotel_id is present in the request URL, so params[:hotel_id] exists in both new and create actions.
• Building the booking from @hotel.bookings.new establishes the association, so the form includes the necessary hotel_id data (either via the nested form URL or the hidden field).
• Using the association in create guarantees the booking is linked to the correct hotel, even if the hotel_id wasn't explicitly submitted (though it will be, thanks to the form setup).

内容的提问来源于stack exchange，提问作者Vridhi Sahu