ActiveRecord的belongs_to的关联返回nil

我有一个模型Spree::Quotation如下ActiveRecord的belongs_to的关联返回nil

class Spree::Quotation < ActiveRecord::Base 

    has_one :payment_term, -> { where(service_type: 'Spree::Quotation') }, 
      class_name: 'PaymentTerm', 
      foreign_key: 'service_id' 
end

这是PaymentTerm模型

class PaymentTerm < ActiveRecord::Base 

    belongs_to :quotation, -> { where(service_type: 'Spree::Quotation') }, 
      class_name: 'Spree::Quotation', 
      primary_key: 'service_id' 
end

这是payment_terms表的内容

development=# SELECT "payment_terms".* FROM "payment_terms"; 

id | service_id | service_type |  term  | 
----+------------+------------------+--------------+ 
    1 |   1 | Spree::Quotation | 100% upfront | 
(1 row)

现在时我做Spree::Quotation.first.payment_term我收到payment_长期正确

2.1.8 :007 > Spree::Quotation.first.payment_term 
    Spree::Quotation Load (1.0ms) SELECT "spree_quotations".* FROM "spree_quotations" ORDER BY "spree_quotations"."id" ASC LIMIT 1 
    PaymentTerm Load (0.7ms) SELECT "payment_terms".* FROM "payment_terms" WHERE "payment_terms"."service_id" = $1 AND "payment_terms"."service_type" = 'Spree::Quotation' LIMIT 1 [["service_id", 1]] 
=> #<PaymentTerm id: 1, service_id: 1, service_type: "Spree::Quotation", term: "100% upfront",... >

但是当我做PaymentTerm.first.quotation，我越来越nil

2.1.8 :008 > PaymentTerm.first.quotation 
    PaymentTerm Load (0.8ms) SELECT "payment_terms".* FROM "payment_terms" ORDER BY "payment_terms"."id" ASC LIMIT 1 
=> nil

为什么不加载报价？在此先感谢

来源

2017-10-21 Tony Vincent

您不必在belongs_to关联中指定条件为payment_terms表具有属性service_id。

class PaymentTerm < ActiveRecord::Base 
    belongs_to :quotation, class_name: 'Spree::Quotation', foreign_key: 'service_id' 
end

来源

2017-10-21 06:28:57

ActiveRecord的belongs_to的关联返回nil

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