Rock'n'Roll Programming: March 2010

Wednesday, March 31, 2010

Apache modules

Modules are either compiled in (static) or dynamically loaded (shared).

List static with httpd -l

List all with httpd -t -D DUMP_MODULES

Shared modules are stored in /etc/httpd/modules/

Shared modules are either loaded directly in httpd.conf or by looking in conf.d/*.conf

E.g. conf.d/perl.conf

...

LoadModule perl_module modules/mod_perl.so

...

Here are some paths that are good to know (Apache on CentOS):

Executables /usr/sbin

Config /etc/httpd

Logs /etc/httpd/log

Web Root /var/www/html

Thursday, March 25, 2010

CSS resources

SohTanaka

Kuler by Adobe

Kuler is an excellent app from Adobe for color exploration.

Try Create->From an Image...

Saturation is a free iPhone app for exploring existing themes.

Tuesday, March 23, 2010

HTML::FormFu select

When using a FormFu select for a simple relation it is easy to display other item names than the default:

The element looks like:

{

label => 'collection',
type => 'Select',
name => 'collection_id',
options => [ map { [ $_->id, $_->collection . ' - ' . $_->product->product ] }
$c->model('PB::Collections')->search( {}, {order_by => 'product.product, collection', prefetch => 'product'} )->all() ],
constraints => [ 'Required' ],
},

But when using a many to many relation in the listbox it becomes trickier, you have to add an accessor to the result class:

The element looks like:

{

label => 'items',
type => 'Select',
name => 'items',
db => {
model => 'PB::Items',
label_column => 'description',
m_to_m_column => 'item_id',
attributes => { prefetch => [ {book => 'title' }, {book => 'collection' }, {book => 'format' } ] , order_by => 'title.title, collection.collection, format.format ' },

},
multiple => 1,
size => 20,
},

And the following sub has to be added to the items resultset:
sub description {
$_[0]->book->title->title . ' - ' . $_[0]->book->collection->collection . ' - ' . $_[0]->book->format->format . ' - ' . $_[0]->isbn;
}

Thanks to Wolfgang for explaining this.

DBIx:Class debugging

If you use DBIx::Class and you want to see what the SQL generated looks

like, you can set the environment variable DBIC_TRACE.

% DBIC_TRACE=1 my_programme.pl

And all the SQL will be printed on STDERR.

If you give a filename to the variable, like this

DBIC_TRACE="1=/tmp/sql.debug"

all the statements will be printed in this file.

I got this info from i'm a lumberjaph which is a great blog about web programming in general and also have quite a few posts about perl and catalyst.

HTML::FormFu resources

HTML::FormFu (CPAN)

HTML-FormFu

html-formfu (listserv)

Integrate HTML::FormFu with DBIx::Class :

DBIx::Class::HTML::FormFu (CPAN, depracated, the one we are using)

Catalyst::Controller::HTML::FormFu (CPAN)

HTML::FormFu::Model::DBIC (CPAN)

COALESCE

Since I've got back to SQL recently it's nice to learn new tricks. COALESCE is great for defaulting to a value after for example a left join.

SQL

SELECT bindings.*, COALESCE( ft.binding, bindings.binding ) AS sortable_binding
   FROM bindings
   LEFT OUTER JOIN ( SELECT binding, binding_id FROM bindings_translated WHERE language = ? ) AS ft ON ( ft.binding_id = bindings.id )

DBIx:Class

        $c->stash->{collections} = [ $product->collections( 
 { 
  language   => $c->stash->{language} 
 },
 { 
 '+select'   => \'COALESCE(translations.collection, me.collection) AS  translated_collection',
 join        => [ 'translations' ],
 order_by    => [ 'translated_collection' ],
 }
        )->all() ];