定義「的has_many通過：ASSOCATION」在作用域條件語句通過模型

我有一個模式，它看起來是這樣的：定義「的has_many通過：ASSOCATION」在作用域條件語句通過模型

create_table "customers" do |t| 
    t.integer "customer_number" 
end 

create_table "past_payments" do |t| 
    t.integer "customer_number" 

    t.datetime "transaction_date" 
    t.integer "arbitrary_sequence_number" 
end 

create_table "payment_details" do |t| 
    t.datetime "transaction_date" 
    t.integer "arbitrary_sequence_number" 
end

TL; DR從模式 - 客戶與past_payment通過關聯主/外鍵。當他們的transaction_date和random_sequence_number相等時，PastPayment與單個PaymentDetail相關聯。付款和詳細信息沒有正式的主/外關鍵關係。

這給了我下面的ActiveRecord型號：

class Customer < ActiveRecord::Base 
    has_many :past_payments, foreign_key: :customer_number, primary_key: :customer_number 

    has_many :payment_details, through: :past_payments # unfortunately, broken 
end 

class PastPayment < ActiveRecord::Base 
    has_one :payment_detail, ->(past_payment) { 
    where(arbitrary_sequence_number: past_payment.arbitrary_sequence_number) 
    }, foreign_key: :transaction_date, primary_key: :transaction_date 
end

由於Customer has_many :past_payments和PastPayment has_one :payment_detail，我會認爲有可以是一個Customer has_many :payment_details, through: :past_payments來定義這樣的關聯，但我不能得到那個工作因爲has_one :payment_detail關聯中定義的範圍。

具體而言，撥打電話Customer.payment_details將產生NoMethodError: undefined method 'arbitrary_sequence_number' for #<Customer:0x2i8asdf3>。所以看起來客戶已經通過了我的範圍，而不是PastPayment。

是否可以在客戶上定義has_many :payment_details關聯？難道我做錯了什麼？

爲了清楚起見，我希望能夠說並執行兩個查詢，所以如果有一種方法可以完成那個沒有關聯的問題，我很樂於接受。

注：我無法更改此數據庫。這是其他應用程序寫入的數據庫，我需要從中讀取數據。

與我的問題無關，這裏是我目前正在使用的解決方法。如果沒有辦法正確地使用協會，我很高興有這個解決方案批評：

class Customer < ActiveRecord::Base 
    attr_writer :payment_details 

    def payment_details 
    @payment_details ||= Array(self).with_payment_details.payment_details 
    end 

    module InjectingPaymentData 
    def with_payment_details 
     results = self.to_a 
     return self unless results.first.is_a?(Customer) 

     user_ids = results.collect(&:id) 

     # i've omitted the details of the query, but the idea is at the end of it 
     # we have a hash with the customer_number as a key pointing to an array 
     # of PaymentDetail objects 
     payment_details = PaymentDetails.joins().where().group_by(&:customer_number) 

     results.each do |customer| 
     customer.payment_details = Array(payment_details[customer.customer_number]) 
     end 
    end 
    end 
end 

ActiveRecord::Relation.send(:include, Customer::InjectingPaymentData) 
Array.send(:include, Customer::InjectingPaymentData)

有了這樣的，我可以做的事情一樣以最小的查詢如下：

@customers = Customer.where(id: 0..1000).with_payment_details 
@customers.each { |c| do_something_with_those_payment_details }

問題用那種方法？

來源

2016-08-19 Gray Kemmey

您可以利用此寶石中的ActiveRecord更好地處理「複合主鍵」：https://github.com/composite-primary-keys/composite_primary_keys

class Customer < ActiveRecord::Base 
    has_many :past_payments, foreign_key: :customer_number, primary_key: :customer_number 

    has_many :payment_details, through: :past_payments # this works now 
end 

class PastPayment < ActiveRecord::Base 
    has_one :payment_detail, foreign_key: [:transaction_date, :arbitrary_sequence_number], 
          primary_key: [:transaction_date, :arbitrary_sequence_number] 
end

來源

2016-09-07 21:47:02

定義「的has_many通過：ASSOCATION」在作用域條件語句通過模型

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