Rails 4: ActionController::UrlGenerationError

Question

我有三个模型：

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

这是我的路线：

resources :users do
  resources :administrations
  resources :calendars
end

————————————

更新：

这是我在终端中运行 rake routes 时得到的结果：

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 工作正常。

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

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，因为我的 user_calendar_path.

中同时包含 @user 和 @calendar

显然，我遗漏了一些东西，但我不知道是什么。

有什么想法吗？

Answer 1

您尚未在 calendars#show 方法中设置 @user 和 @calendar。 new 操作可以很好地呈现您的视图，但它不知道如何填充 @user 和 @calendar

参数

Answer 2

这里的问题是，您正在点击映射到您的 calendars#index 操作的 http://localhost:3000/users/1/calendars url，正确的路径是：user_calendars_path 并且它只需要一个参数 user_id，因为它会将您带到用户的索引页面，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：

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

你不能拥有它，因为对于你控制器中的 index 操作，你没有设置 @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，这就是您收到此错误的原因。

简而言之，你不能在你的 index.html.erb:

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

因为它被映射到 calendars#show 操作，相应的视图应该是 show.html.erb 但目前你在 index.html.erb!

中有它

回答你最后一个问题：

In particular, I don't understand the missing required keys: [:id, :user_id] part, since I have both @user and @calendar in my user_calendar_path.

是的，您在控制器中定义了 @user 和 @calendar，但是在 show 方法中并且 user_calendar_path 映射到 calendars#show 方法。但是，嘿！您是从对应于 calendars#index 操作的 index.html.erb 调用它的。那就是你所缺少的。希望现在一切都清楚了:-)

最后，区别很微妙。

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

user_calendar_path 适用于 show，它会将您带到特定用户的特定日历。在这种情况下，您必须在控制器的 show 方法中设置 @user 和 @calendar。

Rails 4: ActionController::UrlGenerationError

Rails 4: ActionController::UrlGenerationError

ruby-on-rails

has-many-through

nested-resources

nested-routes

ruby-on-rails-4