[PEAR-BUG] Req #13783 [Com]: Add factory pattern for filters

Edit report at http://pear.php.net/bugs/bug.php?id=13783&edit=1

 ID:               13783
 Comment by:       [email protected]
 Reported By:      webmaster at dasourcerer dot net
 Summary:          Add factory pattern for filters
 Status:           Open
 Type:             Feature/Change Request
 Package:          Date_Holidays
 Package Version:  CVS
 PHP Version:      Irrelevant
 Roadmap Versions: 
 New Comment:

I would like to discuss and probably implement this as I have need for
it.
Who to contact for design discussion?


Previous Comments:
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[2008-06-23 14:41:56] dasourcerer

I've spent some time thinking about this.
I think the last proposed solution is a good way for single instances of
holiday drivers but exposes too much functionality in other cases. Maybe
it were good to hide this within the composite filter and add a
Date_holidays_Filter_Composite::addFilterById(...) method?

------------------------------------------------------------------------

[2008-06-12 04:11:06] kguest

I think it would be best to have a factory method for filters as a
method of the [base] driver that the filters would relate to - i.e. the
Ireland driver would have a factory method for returning a filter of
[Un]Official holidays observed in Ireland; though this method should be
inherited from the base Driver class.

A use case could be something along the lines of:

include('Date/Holidays.php');

$composite = Date_Holidays::factory('Composite');
$compositeFilter = new Date_Holidays_Filter_Composite();

/* $selectedDrivers is a subset of the result from
Date_Holidays::getInstalledDrivers() */
foreach($selectedDrivers as $driver) {
  $fdriver = Date_Holidays::factory($driver['id']);
  $composite->addDriver($fdriver);
  $filters = $fdriver->getInstalledFilters();
 /* $selectedFilters is a subset of $filters */
  foreach($selectedFilters as $filter) {
    $compositeFilter->AddFilter($filter);
    $$filter = $fdriver->filterFactory($filter);
  }
}



We shouldn't have to search the filesystem for obtaining the actual
data/filter names returned by the getInstalledFilters method - at the
moment only Germany, Ireland and Netherlands subpackages have filters so
there wouldn't be much impact involved in those drivers simply returning
an array containing the names of the relevant/associated filters.

so, similar to getISO3166Codes, we use something like the following
rather than wasting resources searching the file system:

Date_Holidays_Driver_Germany::getInstalledFilters() {
return array('Official', 'Berlin', ....);
}

and the factory method simply creates and dispenses the appropriate
filter.

------------------------------------------------------------------------

[2008-06-11 04:08:05] dasourcerer

So, are there any decissions on this? I'd provide a patch but I am not
really sure where to place the factory method...

------------------------------------------------------------------------

[2008-04-27 09:47:24] dasourcerer

Well, for holiday drivers I can simply go with:

include('Date/Holidays.php');

$composite = Date_Holidays::factory('Composite');
/* $selectedDrivers is a subset of the result from
Date_Holidays::getInstalledDrivers() */
foreach($selectedDrivers as $driver) {
  $composite->addDriver(Date_Holidays::factory($driver['id']));
}

This is very convenient and relatively safe. Now the same for filters
were about this:

include('Date/Holidays/Filter/Composite.php');
$compositeFilter = new Date_Holidays_Filter_Composite();
/* $selectedFilters is a subset of the result from
Date_Holidays::getInstalledFilters() */
foreach($selectedFilters as $filter) {
  @include_once('Date/Holidays/Filter/' . $filter['id]);
  if(class_exists('Date_Holidays_Filter_' . $filter['title'])) {
    $compositeFilter->addFilter(new 'Date_Holidays_Filter' .
$filter['title']());
  }
)

Now this doesn't seem like a big deal at first. Yet I am feeling pretty
uncomfortable with making assumptions on the package structure and other
logic that were better off being handled by the package itself.

Perhaps the Date_Holidays::factory() could be modified to create filters
as well?

------------------------------------------------------------------------

[2008-04-27 09:09:01] doconnor

Can you show us with a bit of psuedocode what you mean by 'pure pain'?

------------------------------------------------------------------------

The remainder of the comments for this report are too long. To view
the rest of the comments, please view the bug report online at
    http://pear.php.net/bugs/bug.php?id=13783

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