MARC::Field - phpMan

NAME
    MARC::Field - Perl extension for handling MARC fields

SYNOPSIS
      use MARC::Field;

      # If your system uses wacky control field tags, add them
      MARC::Field->allow_controlfield_tags('FMT', 'LLE');

      my $field = MARC::Field->new( 245, '1', '0',
           'a' => 'Raccoons and ripe corn / ',
           'c' => 'Jim Arnosky.'
      );
      $field->add_subfields( "a", "1st ed." );

DESCRIPTION
    Defines MARC fields for use in the MARC::Record module. I suppose you
    could use them on their own, but that wouldn't be very interesting.

EXPORT
    None by default. Any errors are stored in $MARC::Field::ERROR, which
    $MARC::Record usually bubbles up to $MARC::Record::ERROR.

CLASS VARIABLES
    extra_controlfield_tags: Some systems (notably Ex Libris's Aleph) throw
    extra control fields in their MARC (e.g., Aleph's MARC-XML tends to have
    a "FMT" control field). We keep a class-level hash to track to track
    them; it can be manipulated with "allow_controlfield_tags" and
    c<disallow_controlfield_tags>.

METHODS
  new()
    The constructor, which will return a MARC::Field object. Typically you
    will pass in the tag number, indicator 1, indicator 2, and then a list
    of any subfield/data pairs. For example:

      my $field = MARC::Field->new(
           245, '1', '0',
           'a' => 'Raccoons and ripe corn / ',
           'c' => 'Jim Arnosky.'
      );

    Or if you want to add a control field (< 010) that does not have
    indicators.

      my $field = MARC::Field->new( '001', ' 14919759' );

  tag()
    Returns the three digit tag for the field.

  set_tag(tag)
    Changes the tag number of this field. Updates the control status
    accordingly. Will "croak" if an invalid value is passed in.

  indicator(indno)
    Returns the specified indicator. Returns "undef" and logs a warning if
    field is a control field and thus doesn't have indicators. If the field
    is not a control field, croaks if the *indno* is not 1 or 2.

  set_indicator($indno, $indval)
    Set the indicator position *$indno* to the value specified by *$indval*.
    Croaks if the indicator position, is invalid, the field is a control
    field and thus doesn't have indicators, or if the new indicator value is
    invalid.

  allow_controlfield_tags($tag, $tag2, ...)
    Add $tags to class-level list of strings to consider valid control
    fields tags (in addition to 001 through 009). Tags must have three
    characters.

  disallow_controlfield_tags($tag, $tag2, ...)
=head2 disallow_controlfield_tags('*')
    Revoke the validity of a control field tag previously added with
    allow_controlfield_tags. As a special case, if you pass the string '*'
    it will clear out all previously-added tags.

    NOTE that this will only deal with stuff added with
    allow_controlfield_tags; you can't disallow '001'.

  is_valid_tag($tag) -- is the given tag valid?
    Generally called as a class method (e.g.,
    MARC::Field->is_valid_tag('001'))

  is_valid_indicator($indval) -- is the given indicator value valid?
    Generally called as a class method (e.g.,
    MARC::Field->is_valid_indicator('4'))

  is_controlfield_tag($tag) -- does the given tag denote a control field?
    Generally called as a class method (e.g.,
    MARC::Field->is_controlfield_tag('001'))

  is_control_field()
    Tells whether this field is one of the control tags from 001-009.

  subfield(code)
    When called in a scalar context returns the text from the first subfield
    matching the subfield code.

        my $subfield = $field->subfield( 'a' );

    Or if you think there might be more than one you can get all of them by
    calling in a list context:

        my @subfields = $field->subfield( 'a' );

    If no matching subfields are found, "undef" is returned in a scalar
    context and an empty list in a list context.

    If the tag is a control field, "undef" is returned and
    $MARC::Field::ERROR is set.

  subfields()
    Returns all the subfields in the field. What's returned is a list of
    list refs, where the inner list is a subfield code and the subfield
    data.

    For example, this might be the subfields from a 245 field:

            (
              [ 'a', 'Perl in a nutshell :' ],
              [ 'b', 'A desktop quick reference.' ],
            )

  data()
    Returns the data part of the field, if the tag number is less than 10.

  add_subfields(code,text[,code,text ...])
    Adds subfields to the end of the subfield list.

        $field->add_subfields( 'c' => '1985' );

    Returns the number of subfields added, or "undef" if there was an error.

  delete_subfield()
    delete_subfield() allows you to remove subfields from a field:

        # delete any subfield a in the field
        $field->delete_subfield(code => 'a');

        # delete any subfield a or u in the field
        $field->delete_subfield(code => ['a', 'u']);

        # delete any subfield code matching a compiled regular expression
        $field->delete_subfield(code => qr/[^a-z0-9]/);

    If you want to only delete subfields at a particular position you can
    use the pos parameter:

        # delete subfield u at the first position
        $field->delete_subfield(code => 'u', pos => 0);

        # delete subfield u at first or second position
        $field->delete_subfield(code => 'u', pos => [0,1]);

        # delete the second subfield, no matter what it is
        $field->delete_subfield(pos => 1);

    You can specify a regex to for only deleting subfields that match:

       # delete any subfield u that matches zombo.com
       $field->delete_subfield(code => 'u', match => qr/zombo.com/);

       # delete any subfield that matches quux
       $field->delete_subfield(match => qr/quux/);

    You can also pass a single subfield label:

      # delete all subfield u
      $field->delete_subfield('u');

  delete_subfields()
    Delete all subfields with a given subfield code. This is here for
    backwards compatibility, you should use the more flexible
    delete_subfield().

  update()
    Allows you to change the values of the field. You can update indicators
    and subfields like this:

      $field->update( ind2 => '4', a => 'The ballad of Abe Lincoln');

    If you attempt to update a subfield which does not currently exist in
    the field, then a new subfield will be appended to the field. If you
    don't like this auto-vivification you must check for the existence of
    the subfield prior to update.

      if ( $field->subfield( 'a' ) ) {
        $field->update( 'a' => 'Cryptonomicon' );
      }

    If you want to update a field that has no indicators or subfields
    (000-009) just call update() with one argument, the string that you
    would like to set the field to.

      $field = $record->field( '003' );
      $field->update('IMchF');

    Note: when doing subfield updates be aware that "update()" will only
    update the first occurrence. If you need to do anything more complicated
    you will probably need to create a new field and use "replace_with()".

    Returns the number of items modified.

  replace_with()
    Allows you to replace an existing field with a new one. You need to pass
    "replace()" a MARC::Field object to replace the existing field with. For
    example:

      $field = $record->field('245');
      my $new_field = new MARC::Field('245','0','4','The ballad of Abe Lincoln.');
      $field->replace_with($new_field);

    Doesn't return a meaningful or reliable value.

  as_string( [$subfields] [, $delimiter] )
    Returns a string of all subfields run together. A space is added to the
    result between each subfield, unless the delimiter parameter is passed.
    The tag number and subfield character are not included.

    Subfields appear in the output string in the order in which they occur
    in the field.

    If $subfields is specified, then only those subfields will be included.

      my $field = MARC::Field->new(
                    245, '1', '0',
                            'a' => 'Abraham Lincoln',
                            'h' => '[videorecording] :',
                            'b' => 'preserving the union /',
                            'c' => 'A&E Home Video.'
                    );
      print $field->as_string( 'abh' ); # Only those three subfields
      # prints 'Abraham Lincoln [videorecording] : preserving the union /'.
      print $field->as_string( 'ab', '--' ); # Only those two subfields, with a delimiter
      # prints 'Abraham Lincoln--preserving the union /'.

    Note that subfield h comes before subfield b in the output.

  as_formatted()
    Returns a pretty string for printing in a MARC dump.

  as_usmarc()
    Returns a string for putting into a USMARC file. It's really only useful
    for "MARC::Record::as_usmarc()".

  clone()
    Makes a copy of the field. Note that this is not just the same as saying

        my $newfield = $field;

    since that just makes a copy of the reference. To get a new object, you
    must

        my $newfield = $field->clone;

    Returns a MARC::Field record.

  warnings()
    Returns the warnings that were created when the record was read. These
    are things like "Invalid indicators converted to blanks".

    The warnings are items that you might be interested in, or might not. It
    depends on how stringently you're checking data. If you're doing some
    grunt data analysis, you probably don't care.

SEE ALSO
    See the "SEE ALSO" section for MARC::Record.

TODO
    See the "TODO" section for MARC::Record.

LICENSE
    This code may be distributed under the same terms as Perl itself.

    Please note that these modules are not products of or supported by the
    employers of the various contributors to the code.

AUTHOR
    Andy Lester, "<andy AT petdance.com>"