通过同一模型的两个 has_many 关系

Posted 2023-03-23

【中文标题】通过同一模型的两个 has_many 关系

【英文标题】：Two has_many relationship through same model

【发布时间】：2016-12-21 00:32:24

【问题描述】：

我遇到了一个我不知道如何解决的问题。

我有三个模型

老师 房间 小时

我需要通过相同的模型关联它们。到目前为止，我有一个名为 schedules 的第四个模型，它有两个外键。 teacher_id 和 hour_id，效果很好，但是我还需要通过这个模型来关联房间。

这是我的代码：

teacher.rb

class Teacher < ApplicationRecord
  scope :active, -> where(deleted_at: nil)
  has_many :schedules, dependent: :destroy
  has_many :lesson_hours, through: :schedules
  has_many :teacher_courses, dependent: :destroy
  has_many :courses, through: :teacher_courses
  has_many :registrations

  def check_associations
    errors.add(:base, "Há matrículas cadastradas com esse professor. Por favor ajuste antes de deletar.") if self.registrations.active.count > 0
    return errors.blank?
  end

  def delete!
    if check_associations
      self.deleted_at = Time.current
      save!
      return true
    else
      return false
    end
  end
end

room.rb

class Room < ApplicationRecord
  scope :active, -> where(deleted_at: nil)
  has_many :room_courses, dependent: :destroy
  has_many :courses, through: :room_courses
  has_many :registrations

  def check_associations
    errors.add(:base, "Há matrículas cadastradas com essa sala. Por favor ajuste antes de deletar.") if self.registrations.active.count > 0
    return errors.blank?
  end

  def delete!
    if check_associations
      self.deleted_at = Time.current
      save!
      return true
    else
      return false
    end
  end
end

lesson_hour.rb

class LessonHour < ApplicationRecord
  scope :active, -> where(deleted_at: nil)
  has_many :schedules, dependent: :destroy
  has_many :teachers, through: :schedules
  has_many :registrations

  def check_associations
    errors.add(:base, "Há matrículas cadastradas nesse horário. Por favor ajuste antes de deletar.") if self.registrations.active.count > 0
    return errors.blank?
  end

  def delete!
    if check_associations
      self.deleted_at = Time.current
      save!
      return true
    else
      return false
    end
  end
end

schedule.rb

class Schedule < ApplicationRecord
  belongs_to :teacher
  belongs_to :lesson_hour
end

所有这些关联都是通过 TeachersController 中的表单构建的

teachers_controller.rb

def set_lesson_days_and_hours
    @lesson_days = LessonHour.select(:weekday)
                             .group(:weekday)
                             .order(:weekday)
                             .to_a
    @lesson_hours = 
    @lesson_days.each do |ld|
      @lesson_hours[ld.weekday] = LessonHour.active
                                            .select(:id, :start_time)
                                            .order(:start_time)
                                            .where(weekday: ld.weekday)
    end
  end

  def teacher_params
    params
      .require(:teacher)
      .permit(:name, :address, :address_number, :address_complement,
              :address_cep, :address_neighborhood, :city, :state, :birthdate,
              :email, :cpf, :rg, :phone, :mobile, :started_date, :bank, :agency,
              :account_number, :gender, lesson_hour_ids: [], course_ids: [])
  end

将课程时间链接到教师的形式如下：

<div class="row teacher-schedule">
    <h4>Disponibilidade</h4>

    <% @lesson_days.each do |ld| %>
    <div class="col-md-2 one-per-line teacher-schedule">
      <span><strong><%= t(:"date.day_names")[ld.weekday] %></strong></span>
      <%= f.collection_check_boxes(:lesson_hour_ids, @lesson_hours[ld.weekday], :id, :start_time) do |check_box| %>
      <%= check_box.label class:"label-checkbox" do %>
      <%= check_box.check_box + check_box.text.strftime("%H:%M") %>
      <% end %>
      <% end %>
    </div>
    <% end %>
  </div>

那么，我的问题是，如何在日程模型中包含房间关联？

提前致谢

【参考方案1】：

当您需要添加两个 has_many 时，您需要指定 foreign_key 和 class_name 以便 rails 可以进行连接。

例子：

class TwoHasMany < ApplicationRecord
  has_many :scheduled_teachers, foreign_key: :teacher_id, class_name: 'Schedule'
  has_many :teachers, through: :scheduled_teachers

  has_many :scheduled_lessons, foreign_key: :lesson_hour_id, class_name: 'Schedule'
  has_many :lesson_hours, through: :scheduled_lessons
end

【讨论】：

很好，谢谢安德烈。但在我看来，我该如何管理它。我的观点是新老师的表格，我需要以相同的表格添加房间和课程时间。到目前为止，我只有一堂课时间。