Question

我有很多这样的关系：

class User < ApplicationRecord
    has_and_belongs_to_many :letter_trackings
end

和

class LetterTracking < ApplicationRecord
    has_and_belongs_to_many :assignees, class_name: "User"
end

我想使用arel来搜索这样的受理人：

users = User.arel_table
letter_trackings = LetterTracking.arel_table

@users = User.where(users[:name].matches("%#{Afsane Fadaei}%"))
@assignees_ids = @users.pluck(:id).uniq
letters_query = letter_trackings[:assignees].in(@assignees_ids)
@letter_trackings = LetterTracking.where(letters_query)

但它会返回此错误：

ActionView::Template::Error (SQLite3::SQLException: no such column: letter_trackings.assignees: SELECT "letter_trackings".* FROM "letter_trackings" WHERE "letter_trackings"."assignees" IN (1189)):

那是因为我不知道如何在 arel 中查询关联（多对多）列。

任何想法？

Answer 1

您需要获取用于创建HABTM关联的联接表，并搜索assignee_id或user_id，以便在信件跟踪中查询受理人。您可以将以下代码段作为参考。我认为联接表是LetterTrackingUsers。

letter_trackings = LetterTracking.arel_table
letter_trackings_users = LetterTrackingUsers.arel_table # here use HABTM table used by you for joining users and letter_trackings

query = letter_trackings_users[:user_id].in(@assignees_ids)  
or 
query = letter_trackings_users[:assignee_id].in(@assignees_ids)

@letter_trackings = LetterTracking.where(letters_query)

使用arel查询关联字段（多对多的实现）

1 个答案: