Question

我按照说明here创建了一个模型课程，其中有一个学生和一个老师（两个模型用户）和一个课程开始日期。

#Lesson Controller
class Lesson < ActiveRecord::Base
  belongs_to :student, class_name => 'User'
  belongs_to :teacher, class_name => 'User'
end

#User Controller
class User < ActiveRecord::Base
  has_many :lessons_to_attend, :class_name => 'Lesson', :foreign_key => 'student_id'
  has_many :lessons_to_teach, :class_name => 'Lesson', :foreign_key => 'teacher_id'
end

迁移顺利进行，因此在页面上我会尝试查询明天学生的课程：

<% @date = 1.day.from_now %>
<%= @date.strftime("%A")%></br>
<%= @date.strftime("%-d/%-m/%y")%>
<% @user.lessons_to_attend.each do |l| %>
   Lesson    
<% end %>

但是当我导航到此页面时，我收到错误Uninitialized constant error Lesson::User

我错过了什么？我将包含用户控制器，以防需要添加内容。

class UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]

  # GET /users
  # GET /users.json
  def index
    @users = User.all
  end

  # GET /users/1
  # GET /users/1.json
  def show
    @user = User.find(params[:id])
  end

  # GET /users/new
  def new
    @user = User.new
  end

  # GET /users/1/edit
  def edit
  end

  # POST /users
  # POST /users.json
  def create
    @user = User.new(user_params)

    respond_to do |format|
      if @user.save
        format.html { redirect_to @user, notice: 'User was successfully created.' }
        format.json { render :show, status: :created, location: @user }
      else
        format.html { render :new }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /users/1
  # PATCH/PUT /users/1.json
  def update
    respond_to do |format|
      if @user.update(user_params)
        format.html { redirect_to @user, notice: 'User was successfully updated.' }
        format.json { render :show, status: :ok, location: @user }
      else
        format.html { render :edit }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /users/1
  # DELETE /users/1.json
  def destroy
    @user.destroy
    respond_to do |format|
      format.html { redirect_to users_url, notice: 'User was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
   # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def user_params
      params[:user]
    end
end

Answer 1

两件事：

belongs_to :student, class_name => 'User'
belongs_to :teacher, class_name => 'User'

class_name上的语法错误。这应该是:class_name => 'User'或class_name: 'User'。

另一件事是我认为您需要在协会的两边设置inverse_of。

class Lesson < ActiveRecord::Base
  belongs_to :student, class_name: 'User', inverse_of: :lessons_to_attend
  belongs_to :teacher, class_name: 'User', inverse_of: :lessons_to_teach
end

class User < ActiveRecord::Base
  has_many :lessons_to_attend, class_name: 'Lesson', foreign_key: 'student_id', inverse_of: :student
  has_many :lessons_to_teach, class_name: 'Lesson', foreign_key: 'teacher_id', inverse_of: :teacher
end

使用关系的未初始化的常量错误

1 个答案: