Rails 4: ActionController::UrlGenerationError

Question

我有三个模特：

class User < ActiveRecord::Base
  has_many :administrations
  has_many :calendars, through: :administrations
end

class Calendar < ActiveRecord::Base
  has_many :administrations
  has_many :users, through: :administrations
end

class Administration < ActiveRecord::Base
  belongs_to :user
  belongs_to :calendar
end

以下是我的路线：

resources :users do
  resources :administrations
  resources :calendars
end

更新：

下面是我在航站楼运行rake routes时得到的信息：

Prefix Verb   URI Pattern                                        Controller#Action
    user_administrations GET    /users/:user_id/administrations(.:format)          administrations#index
                         POST   /users/:user_id/administrations(.:format)          administrations#create
 new_user_administration GET    /users/:user_id/administrations/new(.:format)      administrations#new
edit_user_administration GET    /users/:user_id/administrations/:id/edit(.:format) administrations#edit
     user_administration GET    /users/:user_id/administrations/:id(.:format)      administrations#show
                         PATCH  /users/:user_id/administrations/:id(.:format)      administrations#update
                         PUT    /users/:user_id/administrations/:id(.:format)      administrations#update
                         DELETE /users/:user_id/administrations/:id(.:format)      administrations#destroy
          user_calendars GET    /users/:user_id/calendars(.:format)                calendars#index
                         POST   /users/:user_id/calendars(.:format)                calendars#create
       new_user_calendar GET    /users/:user_id/calendars/new(.:format)            calendars#new
      edit_user_calendar GET    /users/:user_id/calendars/:id/edit(.:format)       calendars#edit
           user_calendar GET    /users/:user_id/calendars/:id(.:format)            calendars#show
                         PATCH  /users/:user_id/calendars/:id(.:format)            calendars#update
                         PUT    /users/:user_id/calendars/:id(.:format)            calendars#update
                         DELETE /users/:user_id/calendars/:id(.:format)            calendars#destroy
                   users GET    /users(.:format)                                   users#index
                         POST   /users(.:format)                                   users#create
                new_user GET    /users/new(.:format)                               users#new
               edit_user GET    /users/:id/edit(.:format)                          users#edit
                    user GET    /users/:id(.:format)                               users#show
                         PATCH  /users/:id(.:format)                               users#update
                         PUT    /users/:id(.:format)                               users#update
                         DELETE /users/:id(.:format)                               users#destroy
                    root GET    /                                                  static_pages#home

更新2

这是我的calendars_controller.rb文件：

class CalendarsController < ApplicationController
  before_action :set_calendar, only: [:show, :edit, :update, :destroy]

  # GET /calendars
  # GET /calendars.json
  def index
    @calendars = Calendar.all
  end

  # GET /calendars/1
  # GET /calendars/1.json
  def show
  end

  # GET /calendars/new
  def new
    @user = User.find(params[:user_id])
    @calendar = @user.calendars.new
  end

  # GET /calendars/1/edit
  def edit
    @user = User.find(params[:user_id])
    @calendar = @user.calendar.find(params[:calendar_id])
  end

  # POST /calendars
  # POST /calendars.json
  def create
    @user = User.find(params[:user_id])
    @calendar = @user.calendars.new(calendar_params)

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

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

  # DELETE /calendars/1
  # DELETE /calendars/1.json
  def destroy
    @calendar.destroy
    respond_to do |format|
      format.html { redirect_to calendars_url, notice: 'Calendar was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def calendar_params
      params.require(:calendar).permit(:name)
    end
end

http://localhost:3000/users/1/calendars/new和http://localhost:3000/users/1/calendars/1工作得很好。

但是，每当我尝试访问http://localhost:3000/users/1/calendars时，都会得到以下错误：

ActionController::UrlGenerationError in Calendars#index
Showing /Users/TXC/code/rails/calendy/app/views/calendars/index.html.erb where line #17 raised:

No route matches {:action=>"show", :controller=>"calendars", :id=>nil, :user_id=>nil} missing required keys: [:id, :user_id]
Extracted source (around line #17):

      <tr>
        <td><%= calendar.name %></td>
        <td><%= link_to 'Show', user_calendar_path(@user, @calendar) %></td>
        <td><%= link_to 'Edit', edit_user_calendar_path(@user, @calendar) %></td>
        <td><%= link_to 'Destroy', calendar, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>

特别是，我不理解missing required keys: [:id, :user_id]部分，因为@user和@calendar都在我的user_calendar_path中。

显然，我错过了什么，但我想不出是什么。

有什么想法吗？

Answer 1

这里的问题是，您正在点击http://localhost:3000/users/1/calendars url，它映射到您的calendars#index操作，正确的路径是：user_calendars_path，它只需要一个param user_id，因为它将带您到用户的索引页面，并将显示数据库中的所有用户日历。

但是，在您的index.html.erb视图中，您有以下内容：

<td><%= link_to 'Edit', edit_user_calendar_path(@user, @calendar) %></td>

因为对于控制器中的index操作，您没有设置@user和@calendar。您可以在show.html.erb中使用它，但不能在index.html.erb中使用。所以，这就是为什么你要得到这个错误。

简单地说，，，你不能把这个放在你的index.html.erb里

<td><%= link_to 'Show', user_calendar_path(@user, @calendar) %></td>

因为这是映射到calendars#show操作的，相应的视图应该是show.html.erb，但是目前您在index.html.erb中有它！

回答您的最后一个问题：

特别是，我不理解缺少的必需键：:id，:user_id部件，因为我的user_calendar_path中同时有@user和@user_calendar_path。

是的，您在控制器中定义了@user和@calendar，但是在show方法和user_calendar_path映射到该calendars#show方法中。但是嘿！您从index.html.erb调用它，它对应于calendars#index操作。这就是你所缺少的。希望现在是清楚的:-)

终于了，差别是微妙的。

user_calendars_path用于index视图，它显示特定用户的所有日历。在这种情况下，您必须在控制器中的@user操作中设置一个index。

user_calendar_path用于show，它将带您查看特定用户的特定日历。在这种情况下，您必须在控制器的@user方法中设置@calendar和show。

Answer 2

您还没有在@user方法中设置calendars#show和@calendar。new操作可以很好地呈现视图，但它不知道如何填充参数voor @user和@calendar