Question

我正在通过Code4Startup airbnb课程（https://code4startup.com/projects/build-airbnb-with-ruby-on-rails-level-1），但我正在尝试根据自己的想法进行调整 - 这是我为当地大学开设的教育课程。我是ruby和stackoverflow的新手，我已经尝试寻找解决方案多年了，但我的问题是我不知道如何正确描述它，所以请解释它就像我5岁！

我收到的错误：

错误似乎表明我的课程模型没有正确构建，或者它以某种方式恢复到列表模型（也许是因为我的course_params不正确？）

NoMethodError in Courses#new
Showing /Users/Jack_R/code/rails/planet_study/app/views/courses/new.html.erb where line #22 raised:

undefined method `type' for #<Listing:0x007fc25da72ea8>
Extracted source (around line #22):
20
21
22

            <div class="form-group">
              <label>Course Type</label>
              <%= f.select :type, [["English Language", "English Language"], ["Culture", "Culture"], ["Sports", "Sports"], ["Tech/Science", "Tech/Science"], ["Adventure", "Adventure"], ["Mixture", "Mixture"]],
                            id: "type", prompt: "Select...", class: "form-control" %>
            </div>
          </div>

我的模特

我有一个User模型，一个Listing模型和一个Course模型（User＆gt; Listing＆gt; Course）：

 class User < ApplicationRecord

    has_many :listings
    has_many :courses, :through => :listings
  end

清单模型：

class Listing < ApplicationRecord
  belongs_to :user
  has_many :courses
end

课程模式：

class Course < ApplicationRecord
  belongs_to :listing
end

课程控制器

class CoursesController < ApplicationController
before_action :set_course, except: [:index, :new, :create]
before_action :authenticate_user!, except: [:show]

  def index
    @courses = current_user.listings.courses
  end

  def new
    @course = current_user.listings.build
  end

  def create
    @course = listings.build(course_params)
    if @course.save
      redirect_to listing_course_path(@course), notice: "Saved..."
    else
      render :new, notice: "Something went wrong..."
    end
  end

  def show

  def listing
  end

  def pricing
  end

  def description
  end

  def photo_upload
  end

  def amenities
  end

  def location
  end

  def update
    if @course.update(course_params)
      flash[:notice] = "Saved..."
    else
      flash[:notice] = "Something went wrong..."
    end
    redirect_back(fallback_location: request.referer)
  end

  private

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

  def room_params
    params.require(:course).permit(:name, :type, :summary, :address, :places, :start_date, :finish_date, :price)
  end

end
end

课程new.html.erb

<div class="panel panel-default">
  <div class="panel-heading">
    Create your course listing
  </div>
  <div class="panel-body">
    <div class="devise-container">

      <%= form_for @course do |f| %>
        <div class="row">
          </div>

          <div class="col_md_4 select">
            <div class="form-group">
              <label>Course Type</label>
              <%= f.select :type, [["English Language", "English Language"], ["Culture", "Culture"], ["Sports", "Sports"], ["Tech/Science", "Tech/Science"], ["Adventure", "Adventure"], ["Mixture", "Mixture"]],
                            id: "type", prompt: "Select...", class: "form-control" %>
            </div>
          </div>

          <div class="col_md_4 select">
            <div class="form-group">
              <label>Places</label>
              <%= f.select :places, [["1", 1], ["2", 2], ["3", 3], ["4", 4], ["5", 5], ["6", 6], ["7", 7]],
                            id: "places", prompt: "Select...", class: "form-control" %>
            </div>
          </div>

        </div>

        <div><%= f.submit "Create My Course", class: "btn btn-primary-green" %></div>
      <% end %>

    </div>
  </div>
</div>

Answer 1

type是Rails中的保留字。您可以创建具有type属性的模型，但在重命名type属性之前，您无法对此模型执行操作。

如果您尝试通过rails控制台创建新记录，则会看到如下消息：

$ rails console
[1] pry(main)> Course.new(name: 'first', type: 'some type')

ActiveRecord :: SubclassNotFound：单表继承机制找不到子类：＆＃39;某种类型＆＃39;。提出此错误是因为列＆＃39;类型＆＃39;保留用于存储类的情况遗产。如果您不打算将此列重命名，请重命名用于存储继承类或覆盖 Course.inheritance_column使用另一列来获取该信息。从 /Users/***/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/activerecord-5.1.4/lib/active_record/inheritance.rb:196:in `find in find_sti_class＆＃39;

如消息所示，您必须重命名type属性才能使用它，只需运行迁移即可更改此名称并编辑创建的文件，如：

$ rails generate migration rename_type_to_type_of

在生成的文件中使用rename_colum方法，首先指定模型，然后指定旧属性名称，然后指定新属性，如：

class RenameTypeToTypeOf < ActiveRecord::Migration[5.1]
  def change
    rename_column :courses, :type, :type_of
  end
end

之后，您可以运行rails db:migrate。注意type_of只是我的一个不好的建议，你可以根据需要调整它。

NoMethodError - Ruby on Rails

1 个答案: