The document provides a tutorial on using the Dancer web framework in Perl. It describes what Dancer is, how to install it and generate a basic application scaffolding. It then explains the directory structure and key files that are generated, including configuration files, templates, static assets, and the main application module. It also demonstrates how to start the development server and test that the basic application is working.

1. Dancing Tutorial
Alberto Manuel Brand˜o Sim˜es
a o
ambs@perl.pt
Braga Geek Nights
March 1st
Alberto Sim˜es
o Dancing Tutorial

2. Part 0: Ballet
Alberto Sim˜es
o Dancing Tutorial

3. What’s Dancer?

4. A micro framework
for writing web applications

5. So, Yet Another Web Framework?

6. Well, yes!

7. CGI.pm webapps are spaghetti

8. Catalyst is HUGE

9. Ruby introduced something different

11. We needed something similar in Perl

12. Definitely

13. And they also imitated us!

14. Available at
http://perldancer.org
and in GitHub.

15. Part 1: Tango
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o Dancing Tutorial

16. Installing
§ ¤
$ sudo cpan Dancer
¦ ¥
or
§ ¤
$ sudo cpan Task : : Dancer
¦ ¥
or yet
§ ¤
$ cpanm −S Task : : Dancer
¦ ¥
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o Dancing Tutorial

17. Bootstrap application
§ ¤
$ dancer −a MyApp
+ MyApp / bin / app . pl
+ MyApp / config . yml
+ MyApp / environments / development . yml
+ MyApp / environments / production . yml
+ MyApp / views / index . tt
+ MyApp / views / layouts / main . tt
+ MyApp / lib / MyApp . pm
+ MyApp / public / javascripts / jquery . js
+ MyApp / public / css / style . css
+ MyApp / public / css / error . css
+ MyApp / public / images / . . .
+ MyApp / public / 5 0 0 . html
+ MyApp / public / 4 0 4 . html
+ MyApp / public / dispatch . fcgi
+ MyApp / public / dispatch . cgi
+ MyApp / Makefile . PL
+ MyApp /t /002 _index_route . t
+ MyApp /t /001 _base . t
¦ ¥
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o Dancing Tutorial

18. What’s inside
§ ¤
+ MyApp / bin / app . pl
¦ ¥
a standalone light server (starts server in port 3000);
also used for fast-cgi or common cgi backends;
§ ¤
+ MyApp / config . yml
+ MyApp / environments / development . yml
+ MyApp / environments / production . yml
¦ ¥
main configuration file (plugins, modules, etc);
configuration files for production and development:
defines what to report, where to report, etc.
Alberto Sim˜es
o Dancing Tutorial

19. What’s inside
§ ¤
+ MyApp / bin / app . pl
¦ ¥
a standalone light server (starts server in port 3000);
also used for fast-cgi or common cgi backends;
§ ¤
+ MyApp / config . yml
+ MyApp / environments / development . yml
+ MyApp / environments / production . yml
¦ ¥
main configuration file (plugins, modules, etc);
configuration files for production and development:
defines what to report, where to report, etc.
Alberto Sim˜es
o Dancing Tutorial

20. What’s inside
§ ¤
+ MyApp / views / index . tt
+ MyApp / views / layouts / main . tt
¦ ¥
Templates and layouts:
templates are page portions/scraps;
layouts are full page designs
(they are automagically filled by the template);
§ ¤
+ MyApp / public / javascripts / jquery . js
+ MyApp / public / css / style . css
+ MyApp / public / css / error . css
+ MyApp / public / images / . . .
¦ ¥
public/static files:
javascript (Dancer ships with jsquery);
cascade style sheets;
images (for default design);
Alberto Sim˜es
o Dancing Tutorial

21. What’s inside
§ ¤
+ MyApp / views / index . tt
+ MyApp / views / layouts / main . tt
¦ ¥
Templates and layouts:
templates are page portions/scraps;
layouts are full page designs
(they are automagically filled by the template);
§ ¤
+ MyApp / public / javascripts / jquery . js
+ MyApp / public / css / style . css
+ MyApp / public / css / error . css
+ MyApp / public / images / . . .
¦ ¥
public/static files:
javascript (Dancer ships with jsquery);
cascade style sheets;
images (for default design);
Alberto Sim˜es
o Dancing Tutorial

22. What’s inside
§ ¤
+ MyApp / public / 5 0 0 . html
+ MyApp / public / 4 0 4 . html
¦ ¥
pages for 500 and 404 errors;
§ ¤
+ MyApp / public / dispatch . fcgi
+ MyApp / public / dispatch . cgi
¦ ¥
wrappers to configure fast-cgi and cgi backends;
will be back on this later (future talk?);
Alberto Sim˜es
o Dancing Tutorial

23. What’s inside
§ ¤
+ MyApp / public / 5 0 0 . html
+ MyApp / public / 4 0 4 . html
¦ ¥
pages for 500 and 404 errors;
§ ¤
+ MyApp / public / dispatch . fcgi
+ MyApp / public / dispatch . cgi
¦ ¥
wrappers to configure fast-cgi and cgi backends;
will be back on this later (future talk?);
Alberto Sim˜es
o Dancing Tutorial

24. What’s inside
§ ¤
+ MyApp / Makefile . PL
+ MyApp /t /002 _index_route . t
+ MyApp /t /001 _base . t
¦ ¥
Main module Makefile:
usefull to make module of your application
Your test suite;
§ ¤
+ MyApp / lib / MyApp . pm
¦ ¥
Your application!
Alberto Sim˜es
o Dancing Tutorial

25. What’s inside
§ ¤
+ MyApp / Makefile . PL
+ MyApp /t /002 _index_route . t
+ MyApp /t /001 _base . t
¦ ¥
Main module Makefile:
usefull to make module of your application
Your test suite;
§ ¤
+ MyApp / lib / MyApp . pm
¦ ¥
Your application!
Alberto Sim˜es
o Dancing Tutorial

26. Part 2: Flamenco
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27. Traffic Control
Your MyApp/lib/MyApp.pm includes:
§ ¤
p a c k a g e MyApp ;
u s e Dancer ’ : s y n t a x ’ ;
our $VERSION = ’ 0 . 1 ’ ;
get ’ / ’ => sub {
template ’ i n d e x ’ ;
};
true ;
¦ ¥
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o Dancing Tutorial

28. How to test it?
Start the standalone server,
§ ¤
[ ambs@rachmaninoff MyApp ] $ bin / app . pl
¦ ¥
that shows debug info,
§ ¤
[ 9 3 8 7 ] core @0 .000017 > loading Dancer : : Handler : : Standalone
handler in / opt / lib / perl5 / site_perl / 5 . 1 2 . 3 / Dancer / Handler . pm l . 39
[ 9 3 8 7 ] core @0 .000442 > loading handler ’ Dancer : : Handler : :
Standalone ’ in / opt / l o c a l / lib / perl5 / site_perl / 5 . 1 2 . 3 / Dancer . pm l . 230
>> Dancer 1 . 3 0 1 1 server 9387 listening on http : / / 0 . 0 . 0 . 0 : 3 0 0 0
subsection { Entering the development dance floor . . . }
¦ ¥
and open a browser in the specified port.
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29. It Works!

30. Route Handlers
A Dancer app is a collection of route handlers;
A route handler is, basically, a sub;
It is bound to an http method;
And to a path or a path pattern;
Example
get ’ / ’ => sub { . . . };
post ’ / s u b m i t / : f i l e ’ => sub { . . . };
del ’ / r e s o u r c e /∗ ’ => sub { . . . };
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o Dancing Tutorial

31. Route Handlers
A Dancer app is a collection of route handlers;
A route handler is, basically, a sub;
It is bound to an http method;
And to a path or a path pattern;
Example
get ’ / ’ => sub { . . . };
post ’ / s u b m i t / : f i l e ’ => sub { . . . };
del ’ / r e s o u r c e /∗ ’ => sub { . . . };
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o Dancing Tutorial

32. Route Handlers
Static patterns (paths):
§ ¤
get ’ / ’ => sub { . . . };
get ’ / a b o u t ’ => sub { . . . };
¦ ¥
Patterns with named tokens:
§ ¤
get ’ / book / : i d ’ => sub {
# do s o m e t h i n g w i t h params −>{i d }
...
};
get ’ / u s e r / : g r o u p / : u i d ’ => sub {
# u s e params −>{u i d } and params −>{g r o u p } h e r e
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

33. Route Handlers
Static patterns (paths):
§ ¤
get ’ / ’ => sub { . . . };
get ’ / a b o u t ’ => sub { . . . };
¦ ¥
Patterns with named tokens:
§ ¤
get ’ / book / : i d ’ => sub {
# do s o m e t h i n g w i t h params −>{i d }
...
};
get ’ / u s e r / : g r o u p / : u i d ’ => sub {
# u s e params −>{u i d } and params −>{g r o u p } h e r e
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

34. Route Handlers
Patterns with anonymous tokens:
§ ¤
get ’ / f i l e / ∗ . ∗ ’ => sub {
my ( $file , $ext ) = splat ;
...
}
get ’ / show /∗/∗ ’ => sub {
my ( $cat , $subcat ) = splat ;
};
¦ ¥
Regular expressions:
§ ¤
get qr { post / ( d+)−(d+)−(d+)} => sub {
my ( $year , $month , $day ) = splat ;
}
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

35. Route Handlers
Patterns with anonymous tokens:
§ ¤
get ’ / f i l e / ∗ . ∗ ’ => sub {
my ( $file , $ext ) = splat ;
...
}
get ’ / show /∗/∗ ’ => sub {
my ( $cat , $subcat ) = splat ;
};
¦ ¥
Regular expressions:
§ ¤
get qr { post / ( d+)−(d+)−(d+)} => sub {
my ( $year , $month , $day ) = splat ;
}
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

36. Part 3: Mambo
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37. Templating
Dancer has plugins for most templating systems:
Mason, Template Toolkit and others.
Default is a Simple template system, built-in Dancer.
Use the template inside the route:
§ ¤
get ’ / u s e r / : name ’ => sub {
template ’ p r o f i l e ’ => { username => params−>{name } } ;
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

38. Templating
Dancer has plugins for most templating systems:
Mason, Template Toolkit and others.
Default is a Simple template system, built-in Dancer.
Use the template inside the route:
§ ¤
get ’ / u s e r / : name ’ => sub {
template ’ p r o f i l e ’ => { username => params−>{name } } ;
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

39. Rerouting
You can reroute by:
Passing the control to the next matching handler:
§ ¤
get ’ / l a z y ’ => sub {
pass and r e t u r n false ;
};
¦ ¥
Redirecting to other URI:
§ ¤
get ’ / f o r b i d d e n ’ => sub {
r e t u r n redirect ’ / b e t t e r / p l a c e ’
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

40. Rerouting
You can reroute by:
Passing the control to the next matching handler:
§ ¤
get ’ / l a z y ’ => sub {
pass and r e t u r n false ;
};
¦ ¥
Redirecting to other URI:
§ ¤
get ’ / f o r b i d d e n ’ => sub {
r e t u r n redirect ’ / b e t t e r / p l a c e ’
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

41. Rerouting
You can reroute by:
Passing the control to the next matching handler:
§ ¤
get ’ / l a z y ’ => sub {
pass and r e t u r n false ;
};
¦ ¥
Redirecting to other URI:
§ ¤
get ’ / f o r b i d d e n ’ => sub {
r e t u r n redirect ’ / b e t t e r / p l a c e ’
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

42. Serving Files
You can serve a static file:
§ ¤
get ’ / dowload / : f i l e ’ => sub {
my $file = params−>{file } ;
pass and r e t u r n false u n l e s s −f $file ;
send_file $file ;
};
¦ ¥
If the content is generated, just change content-type:
§ ¤
get ’ / readme . t x t ’ => sub {
content_type ’ t e x t / p l a i n ’ ;
return ’ this is plain text ’
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

43. Serving Files
You can serve a static file:
§ ¤
get ’ / dowload / : f i l e ’ => sub {
my $file = params−>{file } ;
pass and r e t u r n false u n l e s s −f $file ;
send_file $file ;
};
¦ ¥
If the content is generated, just change content-type:
§ ¤
get ’ / readme . t x t ’ => sub {
content_type ’ t e x t / p l a i n ’ ;
return ’ this is plain text ’
};
¦ ¥
Alberto Sim˜es
o Dancing Tutorial

44. Thanks to Alexis Sukrieh
(I stole some slides)