getting id from inside controller rails - ruby-on-rails

Question

I'm new to rails so I don't know the correct terminology.
I'm trying to get an id of a community from my subscription controller but I'm getting the error undefined method 'community_id' for nil:NilClass
my SubscriptionController.rb:
class SubscriptionsController < ApplicationController
def create
#subscription = Subscription.new(subscription_params)
#subscription.account_id = current_account.id
#subscription.save
redirect_to community_path(#subcription.community_id) //error here
redirect_to community_path(params[:community_id]) // also error below
end
end
def subscription_params
params.require(:subscription).permit(:community_id)
end
error from 2nd line try: No route matches {:action=>"show", :controller=>"communities", :id=>nil}, missing required keys: [:id].
The subscription is saving into the db. What am I doing wrong?

Answer 1

You're making three common rookie misstakes here:
You're assuming that the community_id passed by the user is actually valid and corresponds with an existing record. Never trust user input.
You're assuming that creating the record will always succeed. It won't - and you should always code defensively to handle that condition. For example if the user double clicks the button the second request should fail as it would lead to a duplicate record.
You're redirecting twice. Each request can only have one response and what you would be doing is just overwriting the LOCATION header unless Rails prevented you from doing it with a double render error.
Instead I would do this as a nested route:
# config/routes.rb
resources :communities do
resources :subscriptions, only: [:create]
end
class Account < ApplicationRecord
has_many :subscriptions
# ...
end
class SubscriptionsController < ApplicationController
before_action :set_community, only: [:create]
# POST /communities/1/subscriptions
def create
# I'm assuming that you are ensuring the account is actually signed in your ApplicationController
# note that you don't need to use strong parameters here as you're not mass assigning any parameters
#subscription = current_account.subscriptions.new(
community: #community
)
# Ensure that the user is notified if creating the record fails.
if #subscription.save
redirect_to #community,
success: 'You are now subscribed.'
else
# #todo provide a more specific failure reason
redirect_to #community,
error: 'Could not create subscription. Please try again later.'
end
end
private
def set_community
# this will bail early and return a 404 response if an invalid id is passed.
#community = Community.find(params[:community_id])
end
end
# app/views/communities/show.html.erb
<%= button_to "Subscribe", [#community, :subscriptions], method: :post %>
This places the community_id parameter as part of the URL itself and is how you RESTfully model relations between resources. The relation is explicit instead of tucked away into the request body. If you're ever passing record ids as hidden inputs you're most likely doing it wrong.