Rails 4 nested shallow routes: how to get parent id in child controller?

Question

In my Rails 4 app, there are four models:

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
  has_many: :posts
end

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

class Post < ActiveRecord::Base
  belongs_to :calendar
end

With this routing:

Rails.application.routes.draw do

  root to: 'pages#home'

  devise_for :users, :path => 'account'

  resources :calendars do
    resources :posts, shallow: true
  end

end

Which gives these routes:

Prefix Verb   URI Pattern                                 Controller#Action
                   posts GET    /posts(.:format)                            posts#index
                         POST   /posts(.:format)                            posts#create
                new_post GET    /posts/new(.:format)                        posts#new
               edit_post GET    /posts/:id/edit(.:format)                   posts#edit
                    post GET    /posts/:id(.:format)                        posts#show
                         PATCH  /posts/:id(.:format)                        posts#update
                         PUT    /posts/:id(.:format)                        posts#update
                         DELETE /posts/:id(.:format)                        posts#destroy
                    root GET    /                                           pages#home
        new_user_session GET    /account/sign_in(.:format)                  devise/sessions#new
            user_session POST   /account/sign_in(.:format)                  devise/sessions#create
    destroy_user_session DELETE /account/sign_out(.:format)                 devise/sessions#destroy
           user_password POST   /account/password(.:format)                 devise/passwords#create
       new_user_password GET    /account/password/new(.:format)             devise/passwords#new
      edit_user_password GET    /account/password/edit(.:format)            devise/passwords#edit
                         PATCH  /account/password(.:format)                 devise/passwords#update
                         PUT    /account/password(.:format)                 devise/passwords#update
cancel_user_registration GET    /account/cancel(.:format)                   devise/registrations#cancel
       user_registration POST   /account(.:format)                          devise/registrations#create
   new_user_registration GET    /account/sign_up(.:format)                  devise/registrations#new
  edit_user_registration GET    /account/edit(.:format)                     devise/registrations#edit
                         PATCH  /account(.:format)                          devise/registrations#update
                         PUT    /account(.:format)                          devise/registrations#update
                         DELETE /account(.:format)                          devise/registrations#destroy
       user_confirmation POST   /account/confirmation(.:format)             devise/confirmations#create
   new_user_confirmation GET    /account/confirmation/new(.:format)         devise/confirmations#new
                         GET    /account/confirmation(.:format)             devise/confirmations#show
             user_unlock POST   /account/unlock(.:format)                   devise/unlocks#create
         new_user_unlock GET    /account/unlock/new(.:format)               devise/unlocks#new
                         GET    /account/unlock(.:format)                   devise/unlocks#show
          calendar_posts GET    /calendars/:calendar_id/posts(.:format)     posts#index
                         POST   /calendars/:calendar_id/posts(.:format)     posts#create
       new_calendar_post GET    /calendars/:calendar_id/posts/new(.:format) posts#new
                         GET    /posts/:id/edit(.:format)                   posts#edit
                         GET    /posts/:id(.:format)                        posts#show
                         PATCH  /posts/:id(.:format)                        posts#update
                         PUT    /posts/:id(.:format)                        posts#update
                         DELETE /posts/:id(.:format)                        posts#destroy
               calendars GET    /calendars(.:format)                        calendars#index
                         POST   /calendars(.:format)                        calendars#create
            new_calendar GET    /calendars/new(.:format)                    calendars#new
           edit_calendar GET    /calendars/:id/edit(.:format)               calendars#edit
                calendar GET    /calendars/:id(.:format)                    calendars#show
                         PATCH  /calendars/:id(.:format)                    calendars#update
                         PUT    /calendars/:id(.:format)                    calendars#update
                         DELETE /calendars/:id(.:format)                    calendars#destroy

And finally, here is the content of posts_controller.rb:

class PostsController < ApplicationController
  before_action :set_post, only: [:show, :edit, :update, :destroy]

  # GET /posts
  # GET /posts.json
  def index
    @posts = Post.all
  end

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

  # GET /posts/new
  def new
    @post = Post.new
  end

  # GET /posts/1/edit
  def edit
  end

  # POST /posts
  # POST /posts.json
  def create
    @calendar = Calendar.find(params[:calendar_id])
    @post = @calendar.posts.create(post_params)

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

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

  # DELETE /posts/1
  # DELETE /posts/1.json
  def destroy
    @calendar = Calendar.find(params[:calendar_id])
    @post.destroy
    respond_to do |format|
      format.html { redirect_to calendar_path(@calendar), notice: 'Post was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def post_params
      params.require(:post).permit(:date, :time, :subject, :format, :copy, :media)
    end
end

I keep running into a similar error.

Issue #1: when I try to delete a post from the show.html.erb calendar view:

<h2><%= @calendar.name %> Calendar</h2>

<h3>Posts</h3>
<% if @calendar.posts.any? %>
    <table>
        <tr>
            <th>Date</th>
            <th>Time</th>
            <th>Subject</th>
            <th>Format</th>
            <th>Copy</th>
            <th>Media</th>
        </tr>
  <% @calendar.posts.each do |post| %>
        <tr>
        <td><%= post.date %></td>
            <td><%= post.time %></td>
            <td><%= post.subject %></td>
            <td><%= post.format %></td>
            <td><%= post.copy %></td>
            <td><%= post.media %></td>
        <td><%= link_to 'View', post %></td>
        <td><%= link_to 'Update', edit_post_path(post) %></td>
        <td><%= link_to 'Delete', post, method: :delete, data: { confirm: 'Are you sure?' } %></td>
        </tr>
    </table>
  <% end %>
...

I get:

ActiveRecord::RecordNotFound in PostsController#destroy
Couldn't find Calendar with 'id'=

Issue #2: when I try to update a post from the edit.html.erb post view:

<h1>Editing Post</h1>

<%= render 'form' %>

<%= link_to 'Show', @post %> |
<%= link_to 'Back', posts_path %>

I get:

ActiveRecord::RecordNotFound in PostsController#update
Couldn't find Calendar with 'id'=

Issue #3: when I try to go back to the show.html.erb calendar view from the show.html.erb post view:

<div>
    <p>Date</p>
    <%= @post.date %>
</div>
<div>
    <p>Time</p>
    <%= @post.time %>
</div>
<div>
    <p>Subject</p>
    <%= @post.subject %>
    </div>
<div>
    <p>Format</p>
    <%= @post.format %>
    </div>
<div>
    <p>Copy</p>
    <%= @post.copy %>
</div>
<div>
    <p>Media</p>
    <%= @post.media %>
</div>

<%= link_to 'Edit', edit_post_path(@post) %> |
<%= link_to 'Back', posts_path %>

I get:

ActiveRecord::RecordNotFound in PostsController#show
Couldn't find Calendar with 'id'=

If my interpretation of the errors is correct, every time, the problem seems to be that I cannot retrieve the id of the calendar the post belongs to.

In other words, I cannot retrieve the parent (calendar) id from the child (post) controller.

I believe this is a problem related to my nested shallow resources and the way my links are built in the views.

I can't figure out how to make these links work.

If you could provide me with the solution — and most importantly the reasoning — for one of the three situations described above, I would most definitely be able to come up with the solution for the other two.

Any idea?

Answer 1

I found a solution to each one of my three issues.

Issue #1: I replaced:

format.html { redirect_to calendar_path(@calendar), notice: 'Post was successfully destroyed.' }

with:

format.html { redirect_to calendar_path(@post.calendar_id), notice: 'Post was successfully destroyed.' } 

in posts_controller.rb.

Issue #2: I replaced:

<%= link_to 'Back', posts_path %> 

with:

<%= link_to 'Back', calendar_path(@post.calendar_id) %>

in the edit.html.erb posts view.

Issue #3: I replaced:

<%= link_to 'Back', posts_path %>

with:

calendar_path(@post.calendar_id)

in the show.html.erb posts view