Re: Deleting a subfield using MARC::Record

On Apr 29, 2006, at 1:08 AM, Mark Jordan wrote:
> Edward Summers wrote:
>
>> Deleting subfields is a bit tricky since subfields may repeat, and  
>> sometimes people just want to delete one of them. An unfortunate  
>> state of affairs perhaps.
>
> Yeah, I can see what you're saying, but doesn't that also apply to  
> repeatable fields?

Well yeah it does, and you're right there is a  
MARC::Record::delete_field isn't there. Would having something  
similar to
that in MARC::Field be useful to you?

> If a particular subfield that is one of a repeated set needed to be  
> deleted, it could be identified by a regex or by its order in an  
> array (following object syntax probably not correct):
>
> @subfields = $subject->subfields();
> foreach $notwanted (@subfields) {
>   if ($notwanted =~ /badsubject/) {
>       $notwanted->delete_subfield();
>   }
> }

That could work if subfields were objects, but they're just strings.  
It could simply delete all of them unless a second parameter is  
passed in, which would basically act like a filter:

$field->delete_subfield('a', qr/badsubject/);

An alternative of course is to play fast and loose with the Object  
model and twiddle with $field->_subfields ... this is an array that  
looks like:

	['a', 'foo', 'b', 'bar']

Of course this opens you up to future failure if the internals of  
MARC::Field change at some point in the future. Which may not be all  
that likely :-)

//Ed