CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-4
ARTLoe
ARTLoe

Reputation: 1799

scope for associations - Rails 4

I would really appreciate if someoneone could help me write a scope displaying the number of females (women) attending an event.

Models

user.rb

belongs_to :category_gender
has_many :payments

category_gender.rb

has_many :users

event.rb

belongs_to :user
has_many :payments

payment.rb

belongs_to :user
belongs_to :event

Terminal

event = Event.find(7)
event_payments = event.payments

2.3.0 :054 > event_payments
[
    [0] #<Payment:0x007fea72ac5b70> {
                               :id => 6,
                            :email => "[email protected]",
                          :user_id => 4,
                        :reference => "SPz_ruZ5om",
                       :created_at => Wed, 16 Nov 2016 13:52:23 UTC +00:00,
                       :updated_at => Wed, 16 Nov 2016 13:52:23 UTC +00:00,
                         :event_id => 7,
               :stripe_customer_id => "cus_9YuZZAniFCZVxn",
                :stripe_payment_id => "ch_19GTpnAAe71J3vK0aj1gKryO",
               :event_payment_date => Wed, 16 Nov 2016 13:52:23 UTC +00:00,
                           :status => "success"
    }
    [1] #<Payment:0x007fea72ac5b70> {
                               :id => 7,
                            :email => "[email protected]",
                          :user_id => 5,
                        :reference => "SPz_mnX4ul",
                       :created_at => Wed, 16 Nov 2016 13:52:23 UTC +00:00,
                       :updated_at => Wed, 16 Nov 2016 13:52:23 UTC +00:00,
                         :event_id => 7,
               :stripe_customer_id => "cus_6FhLLMotYCCYvn",
                :stripe_payment_id => "ch_20GTunDDt87J3vK1sp4gPry9",
               :event_payment_date => Wed, 16 Nov 2016 13:52:23 UTC +00:00,
                           :status => "success"
    }
]

How do I write a scope to find all the payments made by females under an event?

If I write the below I can find the first payment made by a woman:

event.payments.first.user.category_gender.name

2.3.0 :026 > event.payments.first.user.category_gender.name
  Payment Load (0.2ms)  SELECT  "payments".* FROM "payments" WHERE "payments"."event_id" = ?  ORDER BY "payments"."id" ASC LIMIT 1  [["event_id", 7]]
  User Load (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1  [["id", 4]]
  CategoryGender Load (0.1ms)  SELECT  "category_genders".* FROM "category_genders" WHERE "category_genders"."id" = ? LIMIT 1  [["id", 2]]
 => "Female"

I tried the below scope to display all the payments made by females for an event, but no luck - tried a method as well but no luck. Your help and explanation would be much appreciated on who to write this as a scope and a method:

event.rb

scope :females, -> { joins(payment: :category_gender).where('category_genders.name' => "Female") }

def females
  self.payments.where('user.category_gender.name = ?', "Female")
end

error message:

2.3.0 :004 >   event.females
  Payment Load (1.7ms)  SELECT "payments".* FROM "payments" WHERE "payments"."event_id" = ? AND (user.category_gender.name = 'Female')  [["event_id", 7]]
SQLite3::SQLException: no such column: user.category_gender.name: SELECT "payments".* FROM "payments" WHERE "payments"."event_id" = ? AND (user.category_gender.name = 'Female')
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: user.category_gender.name: SELECT "payments".* FROM "payments" WHERE "payments"."event_id" = ? AND (user.category_gender.name = 'Female')

Upvotes: 1

Views: 26

Answers (1)

Andrey Deineko
Andrey Deineko

Reputation: 52357

class Payment
  scope :by_females, -> { joins(user: :category_gender).where(category_genders: { name: 'Female' }) }
end

Now easy usage:

event.payments.by_females

Upvotes: 3

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