Question

在Rails 3.2.21应用程序中，我有这些简单的类：

class Country < ActiveRecord::Base

  default_scope -> do
    where("country_translations.locale = ?", I18n.locale).
      order("country_translations.name").includes(:translations)
  end

  has_many :regions
  has_many :cities
  has_many :translations

  attr_accessible :name, :city_ids
  active_admin_translates :name
end

class Region < ActiveRecord::Base
  default_scope -> do
    where("region_translations.locale = ?", I18n.locale).
      order("region_translations.name").includes(:translations)
  end

  belongs_to :country
  has_many :cities

  attr_accessible :country, :name, :country_id, :city_ids
  active_admin_translates :name
end

当我Country.first.region_ids时，我有这个错误：

ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  missing FROM-clause entry for table "region_translations"
LINE 1: ...regions"  WHERE "regions"."country_id" = 602 AND (region_tra...
                                                         ^
: SELECT "regions".id FROM "regions"  WHERE "regions"."country_id" = 602 AND (region_translations.locale = 'en') ORDER BY region_translations.name
from /home/dougui/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activerecord-3.2.21/lib/active_record/connection_adapters/postgresql_adapter.rb:1163:in `exec'

正如您所看到的，在SQL请求中，似乎不包括region_translations。因此，它无法在订单条款中找到它。它似乎忽略了包含。

Country.first.regions.map(&:id)可以运作，但这是一个糟糕的黑客攻击。

你有更好的解决方案吗？

Answer 1

您应同时使用joins和includes。这将处理性能和错误。

获取has_many关联忽略包含的ID

1 个答案: