ActiveRecord includes not working with foreign keys

问题

I am having a hard time getting table associations to work properly. I have 2 classes (tables) that I need to associate with each other.

class CaseModel < ActiveRecord::Base
    self.primary_key = 'seq_id'
    has_many :model, foreign_key: 'model_seq_id'
end

class Model < ActiveRecord::Base

  self.primary_key = 'seq_id'
  self.table_name = 'model'

  belongs_to :case_model, foreign_key: 'seq_id'
  scope :with_case_info, ->{includes(:case_model)}
end

When I run Model.with_case_info I get the following SQL:

SELECT "CASE_MODEL".* FROM "CASE_MODEL"  WHERE "CASE_MODEL"."SEQ_ID" IN (results from above sql)

What i'm looking for is

SELECT "CASE_MODEL".* FROM "CASE_MODEL"  WHERE "CASE_MODEL"."MODEL_SEQ_ID" IN (results from above sql)

Any help would be appreciated

回答1:

You are pointing to the wrong foreign key in your Model class. The following is correct.

class Model < ActiveRecord::Base

  self.primary_key = 'seq_id'
  self.table_name = 'model'

  belongs_to :case_model, foreign_key: 'model_seq_id'
  scope :with_case_info, ->{includes(:case_model)}
end

On a belongs_to, you're saying that the foreign key is on this model. Based on the has_many in CaseModel, the foreign key is model_seq_id, so Model should use the same foreign key.

回答2:

Im not sure why you are manually specifying the primary and foreign keys. You can simply use has_many and belongs_to and ensure that the Model's table has a case_model_id field and it will work automatically.

来源：https://stackoverflow.com/questions/24685837/activerecord-includes-not-working-with-foreign-keys

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ruby-on-rails

ruby

activerecord