Ruby on rails - 在编写"新"方法时不断"Cannot find Model_name without ID"

Question

作为背景，我目前有三个模型，School, Course和Section，它们都是一对多的关系(School has_many课程和Course has_many部分，在模型中也建立了相应的belongs_to关系)。我还有以下资源(稍后设置排除):

  resources :schools do
    resources :courses
  end
  resources :sections #not part of the nest

虽然sections可以作为嵌套资源的一部分，但我保留了它，因为Rails指南强烈建议只嵌套一层。

所以，我的麻烦是，当它涉及到创建一个新的部分(在SectionsController)，并通过course_id链接到课程

  def new
    @course = Course.find(params[:id]) #this line results in an error
    @section = @course.sections.new
  end

第一行总是会引发"找不到没有ID的课程"错误，尽管尝试了使用:ID，:course_id等的各种不同组合，但我无法通过。因为Course是一个嵌套的资源，还有别的东西，我错过了吗?谢谢你的帮助!

当运行rake routes时，输出如下:

         sections  GET    /sections(.:format)                            sections#index
                   POST   /sections(.:format)                            sections#create
      new_section  GET    /sections/new(.:format)                        sections#new
     edit_section  GET    /sections/:id/edit(.:format)                   sections#edit
          section  GET    /sections/:id(.:format)                        sections#show
                   PUT    /sections/:id(.:format)                        sections#update
                   DELETE /sections/:id(.:format)                        sections#destroy
    school_courses GET    /schools/:school_id/courses(.:format)          courses#index
                   POST   /schools/:school_id/courses(.:format)          courses#create
 new_school_course GET    /schools/:school_id/courses/new(.:format)      courses#new
edit_school_course GET    /schools/:school_id/courses/:id/edit(.:format) courses#edit
     school_course GET    /schools/:school_id/courses/:id(.:format)      courses#show
                   PUT    /schools/:school_id/courses/:id(.:format)      courses#update
                   DELETE /schools/:school_id/courses/:id(.:format)      courses#destroy
           schools GET    /schools(.:format)                             schools#index
                   POST   /schools(.:format)                             schools#create
        new_school GET    /schools/new(.:format)                         schools#new
       edit_school GET    /schools/:id/edit(.:format)                    schools#edit
            school GET    /schools/:id(.:format)                         schools#show
                   PUT    /schools/:id(.:format)                         schools#update
                   DELETE /schools/:id(.:format)                         schools#destroy
              root        /   

Answer 1

由于您的课程与学校嵌套，请尝试使用

你的模型应该有

class School < ActiveRecord::base
  has_many :courses
end
class Course < ActiveRecord::base
  belongs_to :school
end

def new
  school = School.find(params[:school_id])
  @course = school.courses.new
  #your code 
end

你可以通过运行

得到更多关于这个路由的信息

rake routes

HTH

Answer 2

您需要在新的section请求中包含这些参数

{:School_id=> some_id, :course_id=>some_id}

这样你就可以用course

获得section绑定

In section controller

 def new
    @school = School.find(params[:school_id])
    @course = @school.courses.where(:id=>params[:course_id]).first
    @section = @course.sections.new
  end