In this article, I'll walk through a basic Rails (4.0.0) setup for creating a nested resource for two models. Nested resources work well when you want to build out URL structure between two related models, and still maintain a RESTful convention. This code assumes you are running RVM to manage Ruby/Gem versions, and Git for version control.
$ rails new family
$ git init
$ git add .
$ git commit -am "new rails project"# Parent model
$ rails generate scaffold Parent name:string
$ git add .
$ git commit -am "rails generate scaffold Parent name:string children:has_many"
# Child model
$ rails generate scaffold Child name:string parent_id:integer
$ git add .
$ git commit -am "rails generate scaffold Child name:string parent:belongs_to"
# Create db (defaults to SQLite3)
$ rake db:migrate
# version control
$ git add .
$ git commit -m "created resources"$ rake routes
children GET /children(.:format) children#index
POST /children(.:format) children#create
new_child GET /children/new(.:format) children#new
edit_child GET /children/:id/edit(.:format) children#edit
child GET /children/:id(.:format) children#show
PUT /children/:id(.:format) children#update
DELETE /children/:id(.:format) children#destroy
parents GET /parents(.:format) parents#index
POST /parents(.:format) parents#create
new_parent GET /parents/new(.:format) parents#new
edit_parent GET /parents/:id/edit(.:format) parents#edit
parent GET /parents/:id(.:format) parents#show
PUT /parents/:id(.:format) parents#update
DELETE /parents/:id(.:format) parents#destroy# file: config/routes.rb
- resources :parents
- resources :children
+ resources :parents do
+ resources :children
+ end$ rake routes
parent_children GET /parents/:parent_id/children(.:format) children#index
POST /parents/:parent_id/children(.:format) children#create
new_parent_child GET /parents/:parent_id/children/new(.:format) children#new
edit_parent_child GET /parents/:parent_id/children/:id/edit(.:format) children#edit
parent_child GET /parents/:parent_id/children/:id(.:format) children#show
PUT /parents/:parent_id/children/:id(.:format) children#update
DELETE /parents/:parent_id/children/:id(.:format) children#destroy
parents GET /parents(.:format) parents#index
POST /parents(.:format) parents#create
new_parent GET /parents/new(.:format) parents#new
edit_parent GET /parents/:id/edit(.:format) parents#edit
parent GET /parents/:id(.:format) parents#show
PUT /parents/:id(.:format) parents#update
DELETE /parents/:id(.:format) parents#destroy$ rails c
> dad = Parent.new(:name => 'Paul')
=> #<Parent id: nil, name: "Paul", created_at: nil, updated_at: nil>
> dad.save
(0.1ms) begin transaction
SQL (20.0ms) INSERT INTO "parents" ("created_at", "name", "updated_at") VALUES (?, ?, ?) [["created_at", Fri, 06 Apr 2012 16:13:17 UTC +00:00], ["name", "Paul"], ["updated_at", Fri, 06 Apr 2012 16:13:17 UTC +00:00]]
(2.4ms) commit transaction
=> true
> son = dad.children.new(:name => 'Eric')
=> #<Child id: nil, name: "Eric", parent_id: 1, created_at: nil, updated_at: nil>
> daughter = dad.children.new(:name => 'Mara')
=> #<Child id: nil, name: "Mara", parent_id: 1, created_at: nil, updated_at: nil>
> dad.save
=> true
> exit# file: app/controllers/children_controller.rb
@@ -1,4 +1,7 @@
class ChildrenController < ApplicationController
+ before_action :set_parent
before_action :set_child, only: [:show, :edit, :update, :destroy]
# GET /children
# GET /children.json
def index
@@ -80,4 +83,11 @@ class ChildrenController < ApplicationController
format.json { head :no_content }
end
end
private
def set_child
- @child = Child.find(params[:id])
+ @child = @parent.children.find(params[:id])
+
+ def set_parent
+ @parent = Parent.find(params[:parent_id])
+ end
+
endAt this point, each controller and view for the Child class model needs to be adjusted (links, redirection, form, etc)
Method: children#index
# file: app/controllers/children_controller.rb
def index
- @children = Child.all
+ @children = @parent.children.all
+ # We need to override the URL for a child, particularly, it should include the parent ID.
+ def child_url(child)
+ return parent_child_path(@parent, child)
+ end# file: app/views/children/index.html.erb
- <td><%= link_to 'Show', child %></td>
- <td><%= link_to 'Edit', edit_child_path(child) %></td>
- <td><%= link_to 'Destroy', child, confirm: 'Are you sure?', method: :delete %></td>
+ <td><%= link_to 'Show', parent_child_path(@parent, child) %></td>
+ <td><%= link_to 'Edit', edit_parent_child_path(@parent, child) %></td>
+ <td><%= link_to 'Destroy', [@parent, child], confirm: 'Are you sure?', method: :delete %></td>
-<%= link_to 'New Child', new_child_path %>
+<%= link_to 'New Child', new_parent_child_path(@parent) %>Method: children#new
# file: app/controllers/children_controller.rb
def new
- @child = Child.new
+ @child = @parent.children.new# file: app/views/children/_form.html.erb
-<%= form_for(@child) do |f| %>
+<%= form_for([@parent, @child]) do |f| %># file: app/views/children/new.html.erb
-<%= link_to 'Back', children_path %>
+<%= link_to 'Back', parent_children_path(@parent) %>Method: children#create
# file: app/controllers/children_controller.rb
def create
- @child = Child.new(params[:child])
+ @child = @parent.children.new(params[:child])
respond_to do |format|
if @child.save
- format.html { redirect_to @child, notice: 'Child was successfully created.' }
+ format.html { redirect_to [@parent, @child], notice: 'Child was successfully created.' }Method: children#show
# file: app/controllers/children_controller.rb
def show
+ @child = @parent.children.find(params[:id])# file: app/views/children/show.html.erb
-<%= link_to 'Edit', edit_child_path(@child) %> |
-<%= link_to 'Back', children_path %>
+<%= link_to 'Edit', edit_parent_child_path(@parent, @child) %> |
+<%= link_to 'Back', parent_children_path(@parent) %>Method: children#edit
# file: app/controllers/children_controller.rb
def edit
- @child = Child.find(params[:id])
+ @child = @parent.children.find(params[:id])# file: app/views/children/edit.html.erb
-<%= link_to 'Show', @child %> |
-<%= link_to 'Back', children_path %>
+<%= link_to 'Show', parent_child_path(@parent, @child) %> |
+<%= link_to 'Back', parent_children_path(@parent) %>Method: children#update
# file: app/controllers/children_controller.rb
def update
+ @child = @parent.children.find(params[:id])
respond_to do |format|
if @child.update_attributes(params[:child])
- format.html { redirect_to @child, notice: 'Child was successfully updated.' }
+ format.html { redirect_to [@parent, @child], notice: 'Child was successfully updated.' }Method: children#destroy
# file: app/controllers/children_controller.rb
def destroy
+ @child = @parent.children.find(params[:id])
@child.destroy
respond_to do |format|
- format.html { redirect_to children_url }
+ format.html { redirect_to parent_children_path(@parent) }At this point, the default scaffolding's links and redirection have been updated to work with the nested routes.