Rails: No route matches [POST] nested resources - ruby-on-rails

Question

In the routes.rb I have this nested resource
# OBSERVATIVE SESSIONS
resources :observative_sessions do
# OBSERVATIONS
resources :observations
end
In observations_controller.rb
def new
#observative_session = ObservativeSession.find(params[:observative_session_id])
#observation = Observation.new
#observation.observative_session_id = #observative_session.id
end
def create
#observative_session = ObservativeSession.find(params[:observative_session_id])
#observation = #observative_session.observations.build(observation_params)
#observation.user_id = current_user.id
respond_to do |format|
if #observation.save
format.html { redirect_to [#observative_session, #observation], notice: 'Observation was successfully created.' }
format.json { render :show, status: :created, location: #observation }
else
format.html { render :new }
format.json { render json: #observation.errors, status: :unprocessable_entity }
end
end
end
And in observations_controller_test.rb I set up both observation and observative session. The test of new works just fine.
class ObservationsControllerTest < ActionDispatch::IntegrationTest
include Devise::Test::IntegrationHelpers
setup do
#observative_session = observative_sessions(:one)
#observation = observations(:two)
sign_in users(:admin_user)
end
test "should get new" do
get new_observative_session_observation_path(#observative_session)
assert_response :success
end
test "should create observation" do
assert_difference('Observation.count') do
post observative_session_observation_path(#observative_session, #observation), params: { observation: { start_time: #observation.start_time, description: #observation.description, rating: #observation.rating, notes: #observation.notes, celestial_body_name: #observation.celestial_body_name, telescope_name: #observation.telescope_name, binocular_name: #observation.binocular_name, eyepiece_name: #observation.eyepiece_name, filter_name: #observation.filter_name, user_id: #observation.user_id, observative_session_id: #observation.observative_session_id }}
end
But this is the error I get in the creation test
test_should_create_observation
ActionController::RoutingError: No route matches [POST] "/observative_sessions/980190962/observations/298486374"
I can't understand what I'm doing wrong.
Thanks for your help.

Answer 1

When you say POST observation_session_observation_path(#observation_session, #observation) you are telling it to post to a url the has both :observation_session_id and an :id in the params, where the id is that of #obseravtion. However, POST paths for create actions don’t take that last id param (ostensibly you are creating a new record with that action).
Try dropping #observation from your path helper (and make sure you are using the correct create path: observation_session_observations_path(#observation_session).
You can do rake routes to see your routes in your terminal, or localhost:3000/rails/info/routes to see it in the browser.
I also see in your new action you are assigning the observation_session_id manually. I recommend you either do what you do later and call #obervation_session.observations.build, or Observation.new(observation_session: #observation_session). You should avoid setting ids like that.