scope for associations - Rails 4 -

i appreciate if someoneone me write scope displaying number of females (women) attending 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 => "richill@gmail.com",                           :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 => "peter@gmail.com",                           :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 write scope find payments made females under event?

if write below can find first payment made 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".* "payments" "payments"."event_id" = ?  order "payments"."id" asc limit 1  [["event_id", 7]]   user load (0.1ms)  select  "users".* "users" "users"."id" = ? limit 1  [["id", 4]]   categorygender load (0.1ms)  select  "category_genders".* "category_genders" "category_genders"."id" = ? limit 1  [["id", 2]]  => "female"  

i tried below scope display payments made females event, no luck - tried method no luck. , explanation appreciated on write scope , 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".* "payments" "payments"."event_id" = ? , (user.category_gender.name = 'female')  [["event_id", 7]] sqlite3::sqlexception: no such column: user.category_gender.name: select "payments".* "payments" "payments"."event_id" = ? , (user.category_gender.name = 'female') activerecord::statementinvalid: sqlite3::sqlexception: no such column: user.category_gender.name: select "payments".* "payments" "payments"."event_id" = ? , (user.category_gender.name = 'female') 

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

now easy usage:

event.payments.by_females