This are the slides for the Dancer talk I gave at the Perl devroom at FOSDEM 2011. It is more up-to-date than the Pythoners version.

1. Dancer
(the Effortless Perl Web Framework)

2. About me
● Sawyer X
● Sysadmin / Perl Ninja
● Israel.pm / Haifa.pm / TelAviv.pm / Rehovot.pm
● I do system, networking, web, applications, etc.
● http://blogs.perl.org/users/sawyer_x/
● http://search.cpan.org/~xsawyerx/

3. Perl web recap
1995
CGI

4. Perl web recap
2010
Many frameworks
(including micro-frameworks like Dancer)
credit to Dave Rolsky for this intro

5. The big web religions, illustrated

6. Ruby – the fanboys

7. Python – the sticklers

8. PHP – the nonsensical

9. Perl – the nutcases

10. Nutcases?
● Yes, we are insane (but not LISP-insane)
● Insanity is a whole lot of fun!
● Insanity gives us flexibility
● Flexibility gives us cool stuff
● Like Moose and meta-programming
● Like DBIx::Class
● Like Dancer

11. Flask (Pythonese)
from flask import Flask
app = Flask(__name__)
@app.route("/", methods=['GET'])
def hello():
return "Hello World!"
if __name__ == "__main__":
app.run()

12. Dancer (Perlesque)
use Dancer;
get “/” => sub {
“Hello, World!”
};
dance;

13. In comparison
from flask import Flask use Dancer;
app = Flask(__name__)
@app.route("/", methods=['GET']) get “/” => sub {
def hello(): “Hello, World!”
return "Hello World!"
};
if __name__ == "__main__":
app.run() dance;

14. Web development models

15. CGI
● Most common web programming model
● Easy to configure on a web server
● Programmer gets everything in %ENV
● First paragraph in output is for the browser
● Second paragraph is content for the browser
● Error prone, depressing, boring, long

16. MVC
● Separation of Model, View, Controller
● Much more flexible and scalable
● Uses “Namespace Matching”
● Sometimes an over-kill
● MVC framework example: Catalyst

17. Route dispatching
● Succinct
● Clean
● Lightweight
● MVC-ish
● Less enterprisey
● Example: Dancer

18. Dancer treats
● Both read and write, easily!
● Route-based (started as a port of Sinatra)
● PSGI/Plack compliant
● Minimal dependencies
● Any app is also a web server
● CPAN-friendly (<3 CPAN)

19. Recipe for Dancing
● Take an HTTP method
● Add a path to that
● Mix with a subroutine
● And sprinkle plugins and keywords on top

20. Dancer route structure
get '/path' => sub { … };
post '/path' => sub { … };
put '/path' => sub { … };
del '/path' => sub { … };
options '/path' => sub { … };
any '/path' => sub { … };

21. Dancer
● Paths can contain variables
get '/hello/:entity/'
● Support optional variables
get '/hello/:entity?'
● Paths can be Regular Expressions
get qr{/ (w+) / d{2,3} (.+)? }x

22. Dancer login example
post '/login' => sub {
# Validate the username and password
if ( params­>{user} eq 'bob' &&
params­>{pass} eq 'LetMeIn' ) {
session user => params­>{user};
redirect params­>{path} || '/';
} else {
redirect '/login?failed=1';
}
};

23. Templating
get '/' => sub {
template index => {
greeting => 'welcome'
}
};

24. More nifty stuff
● headers 'My­X­Header' => 'Value'
● send_file('report.tar.gz')
● set_cookie name => 'value',
expires => ( time + 3600 ),
domain => 'foo.com'
● status 'not_found'
● to_json, to_yaml, to_xml
● my $file = upload('file_input')
● my $all_uploads = request­>uploads

25. Dancer as Perl philosophy
● Dancer is succinct, efficient and easy to work with
● Dancer is daring
(Probably the only web framework with route caching)
(Websockets in the works!)
● Dancer has a lot of plugins:
(engines for sessions, logging, templates)
● Serializers (JSON, YAML, XML)
● Route filters (before, after, before_template)

26. Oh yeah, route caching...

27. Dancer::Plugin::REST
get '/user/:id.:format' => sub {
UserRS­>find( params­>{id} );
};
# curl http://mywebservice/user/42.json
{ "id": 42, "name": "John Foo",
"email": "john.foo@hopkins.com" }
# curl http://mywebservice/user/42.yml
­­
id: 42
name: "John Foo"
email: "john.foo@hopkins.com"

28. Dancer::Plugin::SiteMap
use Dancer::Plugin::SiteMap;
● You get: /sitemap and /sitemap.xml
● “Yup, it's that simple.”

29. Dancer::Plugin::Email
post '/contact' => sub {
email {
to => 'a@b.com',
subject => 'Test',
message => $msg,
attach => [ path => 'name' ],
}
};

30. Dancer::Plugin::Auth::RBAC
post '/login' => sub {
my $user = params­>{'user'};
my $pass = params­>{'pass'};
if ( auth( $user, $pass ) ) {
if ( auth_asa('guest') ) {...}
if ( auth_can('create') ) {...}
}
};

31. Dancer::Plugin::Ajax
ajax '/check_for_update' => sub {
# some ajax code
};
● Pass if X-Request-With not “XMLHttpRequest”
● Disable the layout
● The action built is a POSTrequest

32. Dancer::Plugin::DBIC
● DBIC (DBIx::Class) – a sophisticated ORM
● Configure the connection in the config file
● Make the ResultSets available in routes

33. Dancer::Plugin::Database
● Database(s) connection in Dancer
get '/widget/view/:id' => sub {
my $sth = database­>prepare(
'select * from widgets where id = ?'
);
$sth­>execute( params­>{id} );
template display_widget => {
widget => $sth­>fetchrow_hashref,
};
};

34. Even more plugins
● Dancer::Plugin::WebSocket
● Dancer::Plugin::FlashMessage
● Dancer::Plugin::Auth::Twitter
● Dancer::Plugin::MobileDevice
● Dancer::Plugin::Feed
● Dancer::Plugin::Redis

35. In culmination
Dancer is beautiful and fun
The way programming should be
PerlDancer.org
search.cpan.org/perldoc?Dancer
http://advent.perldancer.org/2010
(http://advent.perldancer.org/2010/2)

36. Thank you!