Rails Routing And Rendering

Routing and Rendering
An under the hood look at how Rails
receives requests and writes responses

The Router
How Rails decides where to send each request

The Router’s Job
Each time a request comes in, Rails needs to send it to
some action in some controller

The Router’s Job
That’s what the router does

The Router’s Job
The router primarily maps URL’s to actions

The Router’s Job
It may also route based on HTTP verbs

The Router’s Job
It may also route based on HTTP verbs
It can be made to route on additional criteria, like
host name

conﬁg/routes.rb
The routing ﬁle for your application probably
looks something like this by now

ActionController::Routing::Routes.draw do |map|
map.resources :prompts
map.resources :submissions
map.resources :users

map.resource :user_session

map.login "login", :controller => "user_sessions", :action => "new"
map.logout "logout", :controller => "user_sessions", :action => "destroy"

map.activate "activate/:token", :controller => "activations",
:action => "create"

map.connect ':controller/:action/:id'
map.connect ':controller/:action/:id.:format'
end

conﬁg/routes.rb
The routing ﬁle for your application probably
looks something like this by now

The Default Routes
map.connect ':controller/:action/:id.:format'

The Default Routes
These rules support an map.connect ':controller/:action/:id.:format'

older style of Rail
routing
/prompts
/prompts/new
/prompts/create
/prompts/show/1
/prompts/edit/1
/prompts/update/1
/prompts/destroy/1

The Default Routes

older style of Rail
routing
It has fallen out of /prompts
/prompts/new
fashion /prompts/create
/prompts/show/1
/prompts/edit/1
/prompts/update/1
/prompts/destroy/1

The Default Routes

older style of Rail
routing
It has fallen out of /prompts
/prompts/new
fashion /prompts/create
/prompts/show/1
Some people now /prompts/edit/1
/prompts/update/1
remove these rules /prompts/destroy/1

Route Priority

Routes are matches matched in top to bottom order as
they appear in the routes ﬁle

Route Priority

The ﬁrst route to match an incoming request wins

Route Priority

Lower routes may never ﬁre, if a higher route hides
them by matching requests

Route Priority

Lower routes may never ﬁre, if a higher route hides
them by matching requests
This is why the default routes are at the bottom of the
ﬁle: they are the last resort

Resource Routing
map.resources :prompts
map.resources :submissions

Resource Routing
This is the modern map.resources :prompts
Rails routing style map.resources :submissions

GET /prompts
GET /prompts/new
POST /prompts
GET /prompts/1
GET /prompts/1/edit
PUT /prompts/1
DELETE /prompts/1

Resource Routing

You can add non-
standard actions
GET /prompts
GET /prompts/new
POST /prompts
GET /prompts/1
GET /prompts/1/edit
PUT /prompts/1
DELETE /prompts/1

Resource Routing

You can add non-
standard actions
GET /prompts
It routes based on GET /prompts/new
HTTP verbs POST /prompts
GET /prompts/1
GET /prompts/1/edit
PUT /prompts/1
DELETE /prompts/1

Resource Routing

You can add non-
standard actions
GET /prompts
It routes based on GET /prompts/new
HTTP verbs POST /prompts
GET /prompts/1
GET /prompts/1/edit
You get named path/url PUT /prompts/1
DELETE /prompts/1
methods for free

What are HTTP Verbs?
The Web’s transport protocol understands a powerful
language of verbs and objects

Browser’s are generally dumb and do not

They use only GET (links) and POST (forms)

Rails fakes it with browsers using hidden parameters

It also supports the real verbs from smart agents

It also supports the real verbs from smart agents
This is very nice when building API’s

Resource Path Methods
new_user_path()

new_user_path()
GET for new

new_user_path()
GET for new
edit_user_path()

new_user_path()
GET for new
edit_user_path()
GET for edit

new_user_path()
GET for new
edit_user_path()
GET for edit
users_path()

new_user_path()
GET for new
edit_user_path()
GET for edit
users_path()
GET for index

new_user_path()
GET for new
edit_user_path()
GET for edit
users_path()
GET for index
POST for create

new_user_path() user_path(user)
GET for new
edit_user_path()
GET for edit
users_path()
GET for index
POST for create

GET for new GET for show
edit_user_path()
GET for edit
users_path()
GET for index
POST for create

edit_user_path() PUT for update
GET for edit
users_path()
GET for index
POST for create

edit_user_path() PUT for update
GET for edit DELETE for destroy
users_path()
GET for index
POST for create

Singleton Resources

map.resource :user_session

Singleton Resources
A special case of map.resource :user_session
resource routing
GET /user_session/new
POST /user_session
GET /user_session
GET /user_session/edit
PUT /user_session
DELETE /user_session

new_user_session_path
edit_user_session_path
user_session_path

Singleton Resources
resource routing
For unique to the user POST /user_session
GET /user_session
resources GET /user_session/edit
PUT /user_session

user_session_path

Singleton Resources
resource routing
GET /user_session
PUT /user_session
Logins
user_session_path

Singleton Resources
resource routing
GET /user_session
PUT /user_session
Logins
The user’s account new_user_session_path
user_session_path

Singleton Resources
resource routing
GET /user_session
PUT /user_session
Logins
The user’s account new_user_session_path
user_session_path
…

Named Routes
map.login "login",
:controller => "user_sessions",
:action => "new"
map.logout "logout",
:action => "destroy"

map.activate "activate/:token",
:controller => "activations",
:action => "create"

Named Routes

Best for special cases and map.login "login",
pretty URL’s :action => "new"

map.activate "activate/:token",
:controller => "activations",
:action => "create"

Named Routes

login_path is preferred to map.activate "activate/:token",

new_user_session_path :controller => "activations",
:action => "create"

/login
/logout

/activate/5HkeFFwiInKfjA4x25q9

Named Routes


:action => "create"

Email links must GET
/login
/logout

/activate/5HkeFFwiInKfjA4x25q9

Named Routes


:action => "create"

Email links must GET
/login
/logout
You can choose to create
the path method /activate/5HkeFFwiInKfjA4x25q9

Example: A Sign-up Route
We could add a sign-
up route

map.signup "signup",
:controller => "users",
:action => "new"

up route
This would allow us
to use signup_path map.signup "signup",
instead of :controller => "users",
:action => "new"
new_user_path

up route
This would allow us
to use signup_path map.signup "signup",
instead of :controller => "users",
:action => "new"
new_user_path
That would route
to /signup instead
of /users/new

The Root Path

map.root :controller => "prompts",
:action => "index"

The Root Path

Set this path to the
landing page map.root :controller => "prompts",
:action => "index"

http://localhost:3000/
http://myapp.com/

The Root Path

:action => "index"

You have to remove
public/index.html to
get it to work
http://myapp.com/

The Root Path

:action => "index"

You have to remove
public/index.html to
get it to work
http://myapp.com/
This does create a
root_path() method

rake routes
This command shows all of the routes
currently set for your application

prompts GET /prompts(.:format) {:action=>"index", :controller=>"prompts"}
POST /prompts(.:format) {:action=>"create", :controller=>"prompts"}
new_prompt GET /prompts/new(.:format) {:action=>"new", :controller=>"prompts"}
edit_prompt GET /prompts/:id/edit(.:format) {:action=>"edit", :controller=>"prompts"}
prompt GET /prompts/:id(.:format) {:action=>"show", :controller=>"prompts"}
PUT /prompts/:id(.:format) {:action=>"update", :controller=>"prompts"}
DELETE /prompts/:id(.:format) {:action=>"destroy", :controller=>"prompts"}
submissions GET /submissions(.:format) {:action=>"index", :controller=>"submissions"}
POST /submissions(.:format) {:action=>"create", :controller=>"submissions"}
new_submission GET /submissions/new(.:format) {:action=>"new", :controller=>"submissions"}
edit_submission GET /submissions/:id/edit(.:format) {:action=>"edit", :controller=>"submissions"}
submission GET /submissions/:id(.:format) {:action=>"show", :controller=>"submissions"}
PUT /submissions/:id(.:format) {:action=>"update", :controller=>"submissions"}
DELETE /submissions/:id(.:format) {:action=>"destroy", :controller=>"submissions"}
users GET /users(.:format) {:action=>"index", :controller=>"users"}
POST /users(.:format) {:action=>"create", :controller=>"users"}
new_user GET /users/new(.:format) {:action=>"new", :controller=>"users"}
edit_user GET /users/:id/edit(.:format) {:action=>"edit", :controller=>"users"}
user GET /users/:id(.:format) {:action=>"show", :controller=>"users"}
PUT /users/:id(.:format) {:action=>"update", :controller=>"users"}
DELETE /users/:id(.:format) {:action=>"destroy", :controller=>"users"}
new_user_session GET /user_session/new(.:format) {:action=>"new", :controller=>"user_sessions"}
edit_user_session GET /user_session/edit(.:format) {:action=>"edit", :controller=>"user_sessions"}
user_session GET /user_session(.:format) {:action=>"show", :controller=>"user_sessions"}
PUT /user_session(.:format) {:action=>"update", :controller=>"user_sessions"}
DELETE /user_session(.:format) {:action=>"destroy", :controller=>"user_sessions"}
POST /user_session(.:format) {:action=>"create", :controller=>"user_sessions"}
login /login {:action=>"new", :controller=>"user_sessions"}
logout /logout {:action=>"destroy", :controller=>"user_sessions"}

rake routes
This command shows all of the routes
currently set for your application

There’s More to the Router!
You can add “collection” or “member” actions to the
seven standard resource routes

You can nest resources

Creating routes like: /prompts/1/submissions/1

You can preﬁx routes

Creating routes like: /admin/users/1

Creating routes like: /admin/users/1
…

Rendering a Response
The different ways you can respond to a request
in Rails

What is Rendered?

If an action doesn’t call redirect_to() at some point,
some kind of render() generally takes place

What is Rendered?

If render() is called, Rails will try to satisfy that request

What is Rendered?

Otherwise a default render happens

What is Rendered?

Rails will hunt for a view named for the current action

What is Rendered?

Rails will hunt for a view named for the current action
Rails will try to honor the requested format

The Render Format

Both resource routes and the default routes include an
optional :format parameter

The Render Format

This allows you to visit a URL like: /users/1.json

The Render Format

The requested :format there is JSON instead of the
default HTML

The Render Format

The requested :format there is JSON instead of the
default HTML
Rails also honors the HTTP Accept header

Responding to Formats

def index
@articles = Article.all

respond_to do |format|
format.html # take the default action
format.xml do
render :xml => @articles.to_xml
end
format.json do
render :json => @articles.to_json
end
end
end


You can use
respond_to to set def index

explicit responses for respond_to do |format|

each format format.xml do
end
format.json do
end
end
end


You can use
respond_to to set def index

explicit responses for respond_to do |format|

each format format.xml do
end
format.json do
ActiveRecord knows render :json => @articles.to_json
end

how to write XML and end
end

JSON

The Accept Header
Note how the responses changed as I modiﬁed
the header but hit the URL

$ curl http://localhost:3000/articles
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
…
$ curl -H 'Accept: application/xml' http://localhost:3000/articles
<?xml version="1.0" encoding="UTF-8"?>
<articles type="array">
<article>
…
$ curl -H 'Accept: application/json' http://localhost:3000/articles
[{"article":{"updated_at":"2010-03-05T16:08:33Z",…}}]

The Accept Header
Note how the responses changed as I modiﬁed
the header but hit the URL

Atom Feeds

A very popular use of response formats is to create
Atom feeds

Atom Feeds

Atom feeds
Rails adds a little syntactic sugar for this with some
helper methods and the use of the Builder library

Atom Feeds

Atom feeds
Rails adds a little syntactic sugar for this with some
helper methods and the use of the Builder library
Builder allows you to generate XML with a Ruby DSL

Rendering Atom
I’ve added the format and set an ordering that
will help us set good Atom dates

def index
@articles = Article.all(:order => "created_at DESC")

respond_to do |format|
format.atom # take the default action
format.xml do
end
format.json do
end
end
end

Rendering Atom
I’ve added the format and set an ordering that
will help us set good Atom dates

XML With Builder
Builder generates XML (or Atom) from
the nested structure of Ruby blocks

atom_feed do |feed|
feed.title("My Blog Articles")
feed.updated(@articles.ﬁrst.created_at)

@articles.each do |article|
feed.entry(article) do |entry|
entry.title(article.title)
entry.content(article.body, :type => 'html')

entry.author do |author|
author.name("JEG2") # article.user.name
end
end
end
end

XML With Builder
Builder generates XML (or Atom) from
the nested structure of Ruby blocks

An Atom Feed
Rails does a lot of work for us:
adding ID’s and links, converting dates, …

$ curl -H 'Accept: application/atom+xml' http://localhost:3000/articles
<?xml version="1.0" encoding="UTF-8"?>
<feed xml:lang="en-US" xmlns="http://www.w3.org/2005/Atom">
<id>tag:localhost,2005:/articles</id>
<link type="text/html" rel="alternate" href="http://localhost:3000"/>
<link type="application/atom+xml" rel="self" href="http://localhost:3000/articles"/>
<title>My Blog Articles</title>
<updated>2010-03-05T16:08:33Z</updated>
<entry>
<id>tag:localhost,2005:Article/1</id>
<published>2010-03-05T16:08:33Z</published>
<updated>2010-03-05T16:08:33Z</updated>
<link type="text/html" rel="alternate" href="http://localhost:3000/articles/1"/>
<title>The CRUD</title>
<content type="html">Lorem ipsum…</content>
<author>
<name>JEG2</name>
</author>
</entry>
</feed>

An Atom Feed
Rails does a lot of work for us:
adding ID’s and links, converting dates, …

Support Head Content
I have inserted a placeholder that will allow pages
to insert content into the document head

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8">
<title>
<%= ["My Blog", yield(:page_title)].compact.join(" : ") %>
</title>
<%= yield :head %>
</head>
<body>
<%= yield %>
</body>
</html>

Support Head Content
I have inserted a placeholder that will allow pages
to insert content into the document head

An Auto Discovery Link
Now we can have the HTML page inform our
browser of the existence of the feed

<% content_for :head do %>
<%= auto_discovery_link_tag :atom, :format => :atom %>
<% end %>

<h1>Articles</h1>
<ul>
<%= render @articles %>
</ul>

An Auto Discovery Link
Now we can have the HTML page inform our
browser of the existence of the feed

Discovering the Feed
My browser now recognizes the feed and
allows me to view it

Other Types of Renders

Rails can respond to any Mime Type format


You can also choose to send a ﬁle back to the browser


Or generate data programmatically that is passed as
a ﬁle


Or generate data programmatically that is passed as
a ﬁle
I use this to stream CSV back to browsers

Adding Atom Feeds Lab
Your book has instructions for how to add
a couple of feeds to your application

Rails Routing And Rendering

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