ruby-on-rails - Rails Association 如果 bool 值为真

Question

我有两个模型，一个用户模型和一个类(class)模型

用户模式如下所示:

create_table "users", force: true do |t|
    t.string   "username",                        default: "",    null: false
    t.string   "first_name",                      default: "",    null: false
    t.string   "last_name",                       default: "",    null: false
    t.string   "password_digest",                 default: "",    null: false
    t.string   "email",                           default: "",    null: false
    t.string   "email_unconfirmed",               default: "",    null: false
    t.string   "email_verification_token",        default: "",    null: false
    t.string   "password_reset_token",            default: "",    null: false
    t.datetime "password_reset_token_expires_at"
    t.boolean  "admin",                           default: false
    t.boolean  "teacher",                         default: false
    t.datetime "created_at"
    t.datetime "updated_at"
end

类(class)架构如下所示:

create_table "courses", force: true do |t|
    t.integer  "teacher_id"
    t.string   "name"
    t.text     "description"
    t.datetime "created_at"
    t.datetime "updated_at"
end

和用户模型:

class User < ActiveRecord::Base
    has_many :taught_courses, :foreign_key => :teacher_id 
end

我只想让 teacher/admin bool 值为 true 的用户拥有 taught_courses但据我所知，您不能将关联包装在 if 语句中，因为老师？/管理员？方法不可用，我该如何处理？

Answer 1

我认为你可以这样做:

class User < ActiveRecord::Base
    has_many :taught_courses, -> { where(admin: true, teacher: true)}, :foreign_key => :teacher_id 
end

您可以阅读更多关于 ActiveRecord Conditional Associations 的信息在线，并在此处查看示例:

4.1.3.1 where

The where method lets you specify the conditions that the associated object must meet.

class Order < ActiveRecord::Base
  belongs_to :customer, -> { where active: true }
end

---

更新

如果您要使用其他模型进行验证，您可能需要使用 .joins。但是，考虑到您正在 ping 原始模型，您可能希望使用 ActiveRecord Association Extensions

这些使您可以访问 proxy_association 对象，这使您能够通过内存访问“父”数据:

class User < ActiveRecord::Base
    has_many :taught_courses, :foreign_key => :teacher_id do
        def admins_and_teachers
            user = proxy_association.owner
            where("users.admin = ? AND users.teacher = ?", user.admin, user.teacher)
        end
    end
end

我认为这会奏效；如果没有，那肯定是我要看的路径