Perl Dancer for Python programmers

Dancer
(the Effortless Perl Web Framework)

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/

Perl web recap

1995
CGI

Perl web recap

2010
Many frameworks
(including micro-frameworks like Dancer)

The big web religions, illustrated

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

Flask (Pythonese)
from flask import Flask
app = Flask(__name__)

@app.route("/", methods=['GET'])
def hello():
return "Hello World!"

if __name__ == "__main__":
app.run()

Dancer (Perlesque)
use Dancer;

get “/hi” => sub {
“Hello, World!”
};

dance;

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;

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

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

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

Dancer
● Paths can contain variables
get '/hello/:entity/'

● Paths can be Regular Expressions
get qr{/ (w+) / d{2,3} (.+)? }x

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';
    }
};

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

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

Dancer as Perl philosophy
● Dancer is succinct, efficient and easy to work with
● Dancer is daring
(Do you have route caching in Django?)
(Websockets in near future!)
● Dancer has a lot of plugins:
(engines for sessions, logging, templates)
● Serializers (JSON, YAML, XML)
● Route filters (before, after, before_template)

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"

Dancer::Plugin::SiteMap
use Dancer::Plugin::SiteMap;

● You get: /sitemap and /sitemap.xml
● “Yup, it's that simple.”

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

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

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 POST request

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

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,
   };
};

In culmination
Dancer is beautiful and fun
The way programming should be

PerlDancer.org
search.cpan.org/perldoc?Dancer

Perl Dancer for Python programmers

Perl Dancer for Python programmers

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