Rails 5 - Scope with latest has_many association - ruby-on-rails

Question

I'm creating a filtered table for my user model. I've created a few scopes to filter them. I'm :
class User < ApplicationRecord
has_many :invoices
scope :application_approved, -> { ... }
scope :application_denied, -> { ... }
scope :latest_invoice_paid, -> { ... }
scope :latest_invoice_not_paid, -> { ... }
def self.__self__
self
end
end
and in the controller:
def index
filters = params[:statuses] || {}
application_status = filters[:application_status].presence
payments_status = filters[:payments_status].presence
#vehicles = Vehicle.send(application_status || :__self__)
.send(payment_status || :__self__)
.paginate(:page => params[:page], :per_page => 10)
.order('created_at DESC')
end
All of the filters work in isolation, however when chained, filters that are not applied seem to cancel out the earlier filters.
For example, if I set the filter to only show users who have paid, it works. But if I set the filter to only show users who have been approved/unapproved, all users are returned all the time. It seems as though returning self when a filter is not applied just returns all of the users.
So, how can I skip the scope if a filter is not applied for it?

Answer 1

Something like this should do the trick, it also helps secure your send method. Since only whitelisted methods can be executed. The code below does the following:
First create a whitelist with the allowed keys and allowed values.
Get the params[:statuses] or if it doesn't exist create a new Parameters object.
Permit only the allowed keys.
Remove all key-value instances that don't have whitelisted values.
Convert the allowed parameters into a hash.
Reduce the resulting collection. Start with Vehicle.all and send the whitelisted methods (chaining them together). If a key or value isn't present, it won't be looped over so there is no need to call :__self__, or :itself.
Do the rest of your logic.
def index
whitelist = ActiveSupport::HashWithIndifferentAccess.new(
application_status: %w[application_approved application_denied],
payments_status: %w[latest_invoice_paid latest_invoice_not_paid],
)
filters = params[:statuses] || ActionController::Parameters.new
#vehicles =
filters
.permit(*whitelist.keys)
.select { |key, value| whitelist[key].include?(value) }
.to_h
.reduce(Vehicle.all) { |vehicles, (_key, value)| vehicles.send(value) }
.order(created_at: :desc)
.paginate(page: params[:page], per_page: 10)
end
References:
ActiveSupport::HashWithIndifferentAccess
ActionController::Parameters (permit, select and to_h can all be found here)
Enumerable#reduce
The splat operator * in .permit(*whitelist.keys)