Ruby on rails 轨道5-n+；1简单表单gem中的查询问题

我试图用Bullet gem解决Rails中的每一个n+1问题，但我无法解决这个特殊问题：

\u form.html.erb

<%= simple_form_for([:admin, @course, @lesson]) do |f| %>
  <div class="form-inputs">
    <div class="col-md-6">
    <%= f.input :start_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
    <%= f.input :end_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
       <!--Here is the problem-->
      <%= f.association :room, :label_method => lambda { |room| "#{room.title} (#{room.building.title})"}%>
       <!--Here is the problem-->
    </div>
    <div class="col-md-6">
      <%= f.association :teacher, :label_method => lambda { |teacher| "#{teacher.first_name} #{teacher.last_name}"},
      collection: @course.teachers%>
    </div>
  </div>
<div class="col-md-12">
  <div class="form-actions text-center">
    <%= f.submit class: "btn btn-primary btn-lg" %>
  </div>
</div>
<% end %>

module Admin
  class LessonsController < Admin::AdminController
    helper_method :convert_time, :convert_day
    before_action :set_course
    before_action :set_lesson, only: [:show, :edit, :update, :destroy]

    def index
      @lessons = Lesson.includes(:teacher,:course, :room => :building).where(course_id: @course).paginate(page: params[:page], per_page: 10)
    #  @course_lessons = @course.lessons.paginate(page: params[:page], per_page: 10)

    end

    def new
      #@room = Room.all.includes(:building)
      @lesson = Lesson.new
    end

    def create
      @lesson = Lesson.new(lesson_params)
      @lesson.course = @course
      if @lesson.save
        flash[:success] = "Lesson was created"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'new'
      end
    end

    def edit

    end

    def update
      if @lesson.update(lesson_params)
        flash[:success] = "Lesson was updated"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'edit'
      end

    end

    def show

    end

    def destroy
      @lesson.destroy
      flash[:danger] = "Lesson was deleted"
      redirect_to admin_course_lessons_path(@course)
    end



    private

    def set_course
      @course = Course.find(params[:course_id])
    end

    def set_lesson
      @lesson = Lesson.find(params[:id])
    end

    def lesson_params
      params.require(:lesson).permit(:start_at,:end_at, :room_id, :teacher_id)
    end
  end
end

class Room < ApplicationRecord
  belongs_to :building
  has_many :lessons, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: {case_sensitive: false}
  validates :code, presence: true,
            length: {minimum: 2},
            uniqueness: {case_sensitive: false}
  validates :building_id, presence: true


end

class Building < ApplicationRecord
  has_many :rooms, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: true
  validates :code, presence: true,
            length: {minimum: 3},
            uniqueness: {case_sensitive: false}

end

lambda{room}“{room.title}（{room.building.title}）”}%>
lambda{老师}“{老师.名字}{老师.姓氏}”，
集合：@course.teachers%>

表单被呈现到new.html.erb和edit.html.erb。问题出现在我试图获取room.building.title的房间关联线上

以下是截图：

正如你们所看到的，我只想用它的中心名来显示房间名，但Bullet抛出了一个错误。问题是我正在使用lambda函数，所以在控制器中创建变量并没有帮助（或者至少我不知道如何正确创建它），因为问题发生在选择框中。 这里我包括我的控制器：

课程\u控制器.rb

<%= simple_form_for([:admin, @course, @lesson]) do |f| %>
  <div class="form-inputs">
    <div class="col-md-6">
    <%= f.input :start_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
    <%= f.input :end_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
       <!--Here is the problem-->
      <%= f.association :room, :label_method => lambda { |room| "#{room.title} (#{room.building.title})"}%>
       <!--Here is the problem-->
    </div>
    <div class="col-md-6">
      <%= f.association :teacher, :label_method => lambda { |teacher| "#{teacher.first_name} #{teacher.last_name}"},
      collection: @course.teachers%>
    </div>
  </div>
<div class="col-md-12">
  <div class="form-actions text-center">
    <%= f.submit class: "btn btn-primary btn-lg" %>
  </div>
</div>
<% end %>

module Admin
  class LessonsController < Admin::AdminController
    helper_method :convert_time, :convert_day
    before_action :set_course
    before_action :set_lesson, only: [:show, :edit, :update, :destroy]

    def index
      @lessons = Lesson.includes(:teacher,:course, :room => :building).where(course_id: @course).paginate(page: params[:page], per_page: 10)
    #  @course_lessons = @course.lessons.paginate(page: params[:page], per_page: 10)

    end

    def new
      #@room = Room.all.includes(:building)
      @lesson = Lesson.new
    end

    def create
      @lesson = Lesson.new(lesson_params)
      @lesson.course = @course
      if @lesson.save
        flash[:success] = "Lesson was created"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'new'
      end
    end

    def edit

    end

    def update
      if @lesson.update(lesson_params)
        flash[:success] = "Lesson was updated"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'edit'
      end

    end

    def show

    end

    def destroy
      @lesson.destroy
      flash[:danger] = "Lesson was deleted"
      redirect_to admin_course_lessons_path(@course)
    end



    private

    def set_course
      @course = Course.find(params[:course_id])
    end

    def set_lesson
      @lesson = Lesson.find(params[:id])
    end

    def lesson_params
      params.require(:lesson).permit(:start_at,:end_at, :room_id, :teacher_id)
    end
  end
end

class Room < ApplicationRecord
  belongs_to :building
  has_many :lessons, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: {case_sensitive: false}
  validates :code, presence: true,
            length: {minimum: 2},
            uniqueness: {case_sensitive: false}
  validates :building_id, presence: true


end

class Building < ApplicationRecord
  has_many :rooms, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: true
  validates :code, presence: true,
            length: {minimum: 3},
            uniqueness: {case_sensitive: false}

end

模块管理
类lessonscoontroller：建筑）。其中（课程id:@course）。分页（第页：参数[：页]，每页：10）
#@course\u-lessons=@course.lessons.paginate（第页：参数[：页]，每页：10）
结束
def新
#@房间=房间。全部包括（：建筑）
@新课
结束
def创建
@LESSION=LESSION.new（LESSION_参数）
@lesson.course=@course
如果@lesson.save
flash[：success]=“课程已创建”
重定向到管理课程课程路径（@course）
其他的
呈现“新”
结束
结束
定义编辑
结束
def更新
如果@lesson.update（lesson_参数）
flash[：success]=“课程已更新”
重定向到管理课程课程路径（@course）
其他的
渲染“编辑”
结束
结束
def秀
结束
def销毁
@毁灭
flash[：danger]=“课程已删除”
重定向到管理课程课程路径（@course）
结束
私有的
设定航向
@course=course.find（参数[：course\u id]）
结束
def set_课程
@lesson=lesson.find（参数[：id]）
结束
def参数
参数要求（：课）。许可（：开始时间，：结束时间，：房间id，：教师id）
结束
结束
结束

（在这种情况下，与我们相关的行动是新的和编辑的）

以下是相关模型：

room.rb

<%= simple_form_for([:admin, @course, @lesson]) do |f| %>
  <div class="form-inputs">
    <div class="col-md-6">
    <%= f.input :start_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
    <%= f.input :end_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
       <!--Here is the problem-->
      <%= f.association :room, :label_method => lambda { |room| "#{room.title} (#{room.building.title})"}%>
       <!--Here is the problem-->
    </div>
    <div class="col-md-6">
      <%= f.association :teacher, :label_method => lambda { |teacher| "#{teacher.first_name} #{teacher.last_name}"},
      collection: @course.teachers%>
    </div>
  </div>
<div class="col-md-12">
  <div class="form-actions text-center">
    <%= f.submit class: "btn btn-primary btn-lg" %>
  </div>
</div>
<% end %>

module Admin
  class LessonsController < Admin::AdminController
    helper_method :convert_time, :convert_day
    before_action :set_course
    before_action :set_lesson, only: [:show, :edit, :update, :destroy]

    def index
      @lessons = Lesson.includes(:teacher,:course, :room => :building).where(course_id: @course).paginate(page: params[:page], per_page: 10)
    #  @course_lessons = @course.lessons.paginate(page: params[:page], per_page: 10)

    end

    def new
      #@room = Room.all.includes(:building)
      @lesson = Lesson.new
    end

    def create
      @lesson = Lesson.new(lesson_params)
      @lesson.course = @course
      if @lesson.save
        flash[:success] = "Lesson was created"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'new'
      end
    end

    def edit

    end

    def update
      if @lesson.update(lesson_params)
        flash[:success] = "Lesson was updated"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'edit'
      end

    end

    def show

    end

    def destroy
      @lesson.destroy
      flash[:danger] = "Lesson was deleted"
      redirect_to admin_course_lessons_path(@course)
    end



    private

    def set_course
      @course = Course.find(params[:course_id])
    end

    def set_lesson
      @lesson = Lesson.find(params[:id])
    end

    def lesson_params
      params.require(:lesson).permit(:start_at,:end_at, :room_id, :teacher_id)
    end
  end
end

class Room < ApplicationRecord
  belongs_to :building
  has_many :lessons, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: {case_sensitive: false}
  validates :code, presence: true,
            length: {minimum: 2},
            uniqueness: {case_sensitive: false}
  validates :building_id, presence: true


end

class Building < ApplicationRecord
  has_many :rooms, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: true
  validates :code, presence: true,
            length: {minimum: 3},
            uniqueness: {case_sensitive: false}

end

教室

building.rb

<%= simple_form_for([:admin, @course, @lesson]) do |f| %>
  <div class="form-inputs">
    <div class="col-md-6">
    <%= f.input :start_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
    <%= f.input :end_at, minute_step: 5, start_year: Date.today.year %>
    </div>
    <div class="col-md-6">
       <!--Here is the problem-->
      <%= f.association :room, :label_method => lambda { |room| "#{room.title} (#{room.building.title})"}%>
       <!--Here is the problem-->
    </div>
    <div class="col-md-6">
      <%= f.association :teacher, :label_method => lambda { |teacher| "#{teacher.first_name} #{teacher.last_name}"},
      collection: @course.teachers%>
    </div>
  </div>
<div class="col-md-12">
  <div class="form-actions text-center">
    <%= f.submit class: "btn btn-primary btn-lg" %>
  </div>
</div>
<% end %>

module Admin
  class LessonsController < Admin::AdminController
    helper_method :convert_time, :convert_day
    before_action :set_course
    before_action :set_lesson, only: [:show, :edit, :update, :destroy]

    def index
      @lessons = Lesson.includes(:teacher,:course, :room => :building).where(course_id: @course).paginate(page: params[:page], per_page: 10)
    #  @course_lessons = @course.lessons.paginate(page: params[:page], per_page: 10)

    end

    def new
      #@room = Room.all.includes(:building)
      @lesson = Lesson.new
    end

    def create
      @lesson = Lesson.new(lesson_params)
      @lesson.course = @course
      if @lesson.save
        flash[:success] = "Lesson was created"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'new'
      end
    end

    def edit

    end

    def update
      if @lesson.update(lesson_params)
        flash[:success] = "Lesson was updated"
        redirect_to admin_course_lessons_path(@course)
      else
        render 'edit'
      end

    end

    def show

    end

    def destroy
      @lesson.destroy
      flash[:danger] = "Lesson was deleted"
      redirect_to admin_course_lessons_path(@course)
    end



    private

    def set_course
      @course = Course.find(params[:course_id])
    end

    def set_lesson
      @lesson = Lesson.find(params[:id])
    end

    def lesson_params
      params.require(:lesson).permit(:start_at,:end_at, :room_id, :teacher_id)
    end
  end
end

class Room < ApplicationRecord
  belongs_to :building
  has_many :lessons, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: {case_sensitive: false}
  validates :code, presence: true,
            length: {minimum: 2},
            uniqueness: {case_sensitive: false}
  validates :building_id, presence: true


end

class Building < ApplicationRecord
  has_many :rooms, dependent: :destroy
  before_save {self.title = title.upcase_first}
  before_save {self.code = code.upcase}

  validates :title, presence: true,
            length: { minimum: 3, maximum: 50},
            uniqueness: true
  validates :code, presence: true,
            length: {minimum: 3},
            uniqueness: {case_sensitive: false}

end

班级建设

---

很抱歉这篇长文章和我的知识不足。我将非常感谢您的反馈。

您可以使用

f.association

中的

includes

指定

集合

选项。像这样：

---

f.association:room，：label_method=>lambda{124; room |“{room.title}（{room.building.title}）”，：collection=>room.includes（：building）。all}

能否尝试在

f.association

中指定

collection

选项，然后使用

includes

来避免N+1查询问题？我的意思是像这样的

f.association:room，：label_method=>lambda{124; room |“{room.title}（{room.building.title}）”，：collection=>room.includes（：building）。all}

是的，解决了这个错误：）我不知道它可以用这种方式解决，非常感谢。（我不知道如何将你的评论标记为解决方案，所以我只是投赞成票）酷，我将把它作为一个答案：）