如何查询Rails 5中的“有多通”关系

Question

我有一个具有以下模型的Rails 5应用程序：

User.rb，Campaign.rb，UserCampaign.rb

关系是User has many Campaigns through UserCampaign。通过这种关系，我可以查询@user.campaigns以查找与该用户相关的所有活动。到目前一切尚好。

UserCampaign模式如下所示：

create_table "user_campaigns", force: :cascade do |t|
  t.bigint "campaign_id"
  t.bigint "user_id"
  t.boolean "responded", default: false
  t.index ["campaign_id"], name: "index_user_campaigns_on_campaign_id"
  t.index ["user_id", "campaign_id"], name: "index_user_campaigns_on_user_id_and_campaign_id"
  t.index ["user_id"], name: "index_user_campaigns_on_user_id"
end

理想情况下，我想编写@user.campaigns.where(responded: false)。但是，我得到以下错误：

PG::UndefinedColumn: ERROR: column campaigns.responded does not exist LINE 1: ...izard_id" WHERE "user_campaigns"."user_id" = $1 AND "campaigns".... ^ : SELECT "campaigns".* FROM "campaigns" INNER JOIN "user_campaigns" ON "campaigns"."id" = "user_campaigns"."campaign_id" WHERE "user_campaigns"."user_id" = $1 AND "campaigns"."responded" = $2

我知道我明白这一点，因为responded是一个关于UserCampaign的专栏，而不是竞选。使连接包含响应列的最佳方法是什么？

Answer 1

PG：：未定义柱:错误:列campaigns.responded不存在

您应该重写您的查询如下

@user.campaigns.joins(:user_campaigns).where(user_campaigns: {responded: false})