Catalyst - refactor large apps with it and have fun!

Catalyst - refactor & have fun – refactor large apps with tE@M (of individuals) and have fun! Adam Bartosik, krakow.pm

What we had? 24 Existing datawarehouse with CGI web interface  365 working (mostly) 24h*365  build by many people  Perl supports individuality  Large projects HATE this 

What we had? Codebase: different styles of programming /  how perl was growing in-line script / eval { main() } / procedural  split into packages  3 approaches to html templates  3 database wrappers  own date-time counting libs  hacks, hacks, hacks.../ bugs, bugs, bugs... 

What we had / we want perl is not too formal a language. Great for  things you need to change, develop the way you've never thought before /what we mostly do/. The bigger a perl project is,  the more rules you need to obey. warnings, strict, perl-critic are just about code  quality, not about design practices XP, test-approach, test-suits - hard to start but  make work easier, safer and faster (changes are welcome!)

What we want? make it the best possible way  make it easier  maintainable  learn something new, have fun :) 

Choosing new platform hours of talking, advocating  use CPAN instead of self-made libs (opposit to  company politic?) they have better doc  better tested  are still being developed  eg. DateTime is slower than simple $date, but  checks ranges SQL::Abstract can quote everything  TT can move view-logic to templates 

web framework needed! we don't like to deal with sessions, url handling,  redirecting (handling simple redirect in cgi is NOT simple) CGI::App is like glue, but we need fundaments  it should be popular enough to have some  support level /work must be done/ so the winner is... 

Catalyst ++ Catalyst – similar to Rails  MVC – code / layout / data source  MUST (/should) be split :) directory layout  can start web app in a minute  most of web tasks (sessions, url mapping,  redirects) are one-liners self server to test changes (quick start for  developers)

Catalyst -- hard to find good doc (but going better)  too flexible, TIMTOWTDI  what to use for O/R mapping?  which templates?  type of config file?  session storage?  view type?  Rails, Django are easier to start with, have  better doc, marketing, hype, ”proper way to do it”

Learning curve ? start-up: first 2-3 weeks are the worst  tutos, docs, advent calendars, Handel, different  approaches, different results logical or a crap we wasting time on? 

Learning curve Template Toolkit make life easier:  pass complex data [ {name=>bar}, {name=>baz} ]  to templates, iterations are done in tpl <ul> [% FOREACH row IN rows %]  <li>[% row.name %] [% END %] </ul> easy Ajax integration  can switch totally different layouts (we needed it 3  months later – nice to be possible do this without big hacks) Don't forget Mason => no another lang in tpl 

Learning curve DBIx::Class – rapid ORM interface  use when it is worth to use  it is not trivial to rewrite complex SQL queries to  dbix, does not simplify complicated joins (we have datawarehouse, a little more than blog – SQL can be simpler) dbix is powerfull for data updating  $post = $c->model('app::comment')->create({  nick => $c->req->{'nick'}, value => $c->req->{'value'} }); $post->update;

Learning curve Easy ”hard CGI things”  dynamic redirect (after save, redirect user to eg.  main page) sub save : Local { my ($self, $c) = @_; # save # redirect $c->res->redirect($c->uri_for('/')); }

Learning curve Global ”catch-flag”, eg:  change language  choose output format  app/Controller/Root.pm sub pdf : Regex('.?pdf$') { my ($self, $c) = @_; my $redir = $c->req->path; $redir =~ s/.pdf$//; $c->stash->{output_pdf} = 1; $redirect =~ s{/$}{/index}; $c->forward($redirect); }

Learning curve Preserve link layout (when SEO matters)  URL: /news/what-about-perl6.html sub news : LocalRegex('^/(.+).html$') { my ($self, $c) = @_; my $title = $c->req->captures->[0]; # find this article by $title... }

Learning curve Still no best answer to all  form/multiform/validation tasks. HTML::Widget  Form::Builder  everything is possible, but typically breaks mvc  MVC: Forms design should be in templates  (view, css, layout), not in controllers, validation rules for input data should be placed in models (see Rails approach)

Learning curve Web-services – SOAP, XML-RPC, REST – to  share data with other systems/projects just output xml/yaml/anything  sub xml : Local { $c->res->body(XMLout($data)); # kiss/works } build simple controller with pure TT and xml  template (fast when you must pass defined output, DTD/Schema) many plugins/controllers in CPAN, eg.  C::P::Flavour, see also Catalyst Cookbook / simply ask what kind of abstraction for WS you need

Catalyst is social! easy to work together – code is split /by design/  into many parts no global switches/routing rules => less  conflicts in code repository the team can scale: start with 2, growth to 5 or  more

Catalyst is social! We must obey some rules & conventions – what,  where, how – work in team need some rules => they make life easier why develop own libs when there are so many  good on CPAN? We can fix bugs, extend them, contribute to open source less own codebase => lower costs  more developers => better approaches  other features => can need them in 2 or 3 months 

Benefits after time Months of active developemt but codebase is  still fresh (and it is perl, true!) Clear design  Only ”business application” code  Less to type  We can make deep changes:  multi-level caches for balanced nodes  with pre-caching change layout as often as is needed by marketing :) 

Benefits after time Catalyst works like a web-processing  meta-language It is not that (dirty) perl, it is a Catalyst 

see in Krakow! Thanks - krakow perl mongers

Catalyst - refactor large apps with it and have fun!

by mold on Sep 01, 2007

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Catalyst - refactor large apps with it and have fun! — Presentation Transcript