Ruby on rails 多态性具有多个关联，并且属于多个关联

我有一个具有以下结构的联接表：

  create_table "enrollment_auth", id: false, force: :cascade do |t|
    t.integer "enrollment_id"
    t.string "authorizable_type"
    t.bigint "authorizable_id"
  end

这里的想法是，我希望将模式中的各种记录与注册相关联（将其视为用户）。以下是我的示例数据：

+---------------+--------------------+------------------+
| ENROLLMENT_ID |  AUTHORIZABLE_TYPE |  AUTHORIZABLE_ID |
+---------------+--------------------+------------------+
|               |                    |                  |
| 1             |  Location          |  1               |
|               |                    |                  |
| 1             |  Location          |  2               |
|               |                    |                  |
| 1             |  Asset             |  8               |
+---------------+--------------------+------------------+

我要寻找的是一个

拥有且属于多个：在我的
注册
模型中验证位置

或

拥有多个

关系，以获得所有特定的多态集。即

注册.last.auth_位置

或

注册.last.auth_资产

等

我有这个，看起来很接近：

  has_and_belongs_to_many :auth_locations, -> { where "enrollment_auth.authorizable_type = 'Location'" }, join_table: :enrollment_auth, class_name: 'Location', association_foreign_key: 'authorizable_id'

在控制台上：

[42] pry(main)> Enrollment.last.auth_location_ids
  Enrollment Load (0.4ms)  SELECT  "enrollments".* FROM "enrollments" ORDER BY "enrollments"."id" DESC LIMIT $1  [["LIMIT", 1]]
   (0.4ms)  SELECT "locations"."id" FROM "locations" INNER JOIN "enrollment_auth" ON "locations"."id" = "enrollment_auth"."authorizable_id" WHERE "locations"."company_id" = 9 AND "enrollment_auth"."enrollment_id" = $1 AND (enrollment_auth.authorizable_type = 'Location')  [["enrollment_id", 99]]
=> []

这是一个空集，因为我还没有任何联接表条目，这是下一个问题。根据文档（）我现在应该能够做到：

[43] pry(main)> Enrollment.last.auth_locations.build(authorizable_id: 12)
  Enrollment Load (0.3ms)  SELECT  "enrollments".* FROM "enrollments" ORDER BY "enrollments"."id" DESC LIMIT $1  [["LIMIT", 1]]
NoMethodError: undefined method `build' for nil:NilClass
from (pry):43:in `__pry__'
[44] pry(main)> 

直接建立一个新的关联，但失败了。我觉得我遗漏了一个小细节