Call create action from different controller - ruby-on-rails

Question

I would like to create a booking from bookings#new and rooms#show. When I try to create it from bookings#new it works, but when try to create it from rooms#show it shows me the error:
1 error prohibited this booking from being saved, room must exist.
Here is the code I'm using:
BookingsController:
def create
if #room
#room = Room.find(params[:room_id])
#booking = #room.bookings.create(booking_params)
if #booking.save
redirect_to room_path(#room)
else
render :new
end
else
#booking = Booking.new(booking_params)
respond_to do |format|
if #booking.save
format.html { redirect_to #booking, notice: 'Booking was successfully created.' }
format.json { render :show, status: :created, location: #booking }
else
format.html { render :new }
format.json { render json: #booking.errors, status: :unprocessable_entity }
end
end
end
end
views/rooms/show.html.erb
<h2>book this room:</h2>
<%= form_with(model: [ #room, #room.bookings.build ], local: true) do |form| %>
<p>
<%= form.label :traveller %>
<%= form.text_field :traveller %>
</p>
<p>
<%= form.label :startfrom %>
<%= form.datetime_select :startfrom %>
</p>
<p>
<%= form.label :endsat %>
<%= form.datetime_select :endsat %>
</p>
<p>
<%= form.label :bookingref %>
<%= form.text_field :bookingref %>
</p>
<p>
<%= form.submit %>
</p>
<% end %>

Answer 1

Your mistake is inside if-else in the controller. You're checking #room before you define it, so it is always nil. It should be:
def create
# use find_by here, otherwise you get RecordNotFound error
#room = Room.find_by(id: params[:room_id])
if #room
# use build, because create saves the instance
#booking = #room.bookings.build(booking_params)
if #booking.save
redirect_to room_path(#room)
else
# I suppose you don't want render bookings/new view here
render 'books/show'
end
else
#booking = Booking.new(booking_params)
respond_to do |format|
# redirect and render logic goes here. BTW, do you really need json response format?
end
end
end
end
Also, define in rooms#show action
#booking = #room.bookings.build
and use the instance in the form to correctly display validation errors
form_with(model: [#room, #booking], local: true) do |form|