Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (Debian-5.0)
Apropos / Subsearch:
optional field

Mail::Field(3pm)      User Contributed Perl Documentation     Mail::Field(3pm)

       Mail::Field - Base class for manipulation of mail header fields

        Mail::Field is extended by

        use Mail::Field;

        my $field = Mail::Field->new('Subject', 'some subject text');
        my $field = Mail::Field->new(Subject => 'some subject text');
        print $field->tag,": ",$field->stringify,"\n";

        my $field = Mail::Field->subject('some subject text');

       "Mail::Field" creates and manipulates fields in MIME headers, collected
       within a Mail::Header object.  Different field types have their own
       sub-class (extension), defining additional useful accessors to the
       field content.

       People are invited to merge their implementation to special fields into
       MailTools, to maintain a consistent set of packages and documentation.


       Mail::Field (and it's sub-classes) define several methods which return
       new objects. These can all be categorized as constructor.


           Take a LIST of "Mail::Field" objects (which should all be of the
           same sub-class) and create a new object in that same class.

       Mail::Field->extract(TAG, HEAD [, INDEX ])

           Takes as arguments the tag name, a "Mail::Head" object and option-
           ally an index.

           If the index argument is given then "extract" will retrieve the
           given tag from the "Mail::Head" object and create a new
           "Mail::Field" based object.  undef will be returned in the field
           does not exist.

           If the index argument is not given the the result depends on the
           context in which "extract" is called. If called in a scalar context
           the result will be as if "extract" was called with an index value
           of zero. If called in an array context then all tags will be
           retrieved and a list of "Mail::Field" objects will be returned.

       Mail::Field->new(TAG [, STRING | OPTIONS])

           Create an object in the class which defines the field specified by
           the TAG argument.

       "Fake" constructors


           This constructor is used internally with preprocessed field infor-
           mation.  When called on an existing object, its original content
           will get replaced.


           Parse a field line.



           Change the settings (the content, but then smart) of this field.


           Returns the field as a string.



           Return the tag (in the correct case) for this item.  Well, actually
           any casing is OK, because the field tags are treated case-insenti-
           tive; however people have some preferences.

       Smart accessors


           Without arguments, the field is returned as stringify() does.  Oth-
           erwise, the STRING is parsed with parse() to replace the object's

           It is more clear to call either stringify() or parse() directly,
           because this method does not add additional processing.


       All sub-classes should be called Mail::Field::name where name is
       derived from the tag using these rules.

       o   Consider a tag as being made up of elements separated by '-'

       o   Convert all characters to lowercase except the first in each ele-
           ment, which should be uppercase.

       o   name is then created from these elements by using the first N char-
           acters from each element.

       o   N is calculated by using the formula :-

               int((7 + #elements) / #elements)

       o   name is then limited to a maximum of 8 characters, keeping the
           first 8 characters.

       For an example of this take a look at the definition of the
       "_header_pkg_name()" subroutine in "Mail::Field"

       Error: Undefined subroutine <method> called

           Mail::Field objects use autoloading to compile new functionality.
           Apparently, the mehod called is not implemented for the specific
           class of the field object.

       This module is part of the MailTools distribution, http://perl.over-

       The MailTools bundle was developed by Graham Barr.  Later, Mark Over-
       meer took over maintenance without development.

       Mail::Cap by Gisle Aas <aasAToslonett.no>.  Mail::Field::AddrList by
       Peter Orbaek <poeATcit.dk>.  Mail::Mailer and Mail::Send by Tim Bunce
       <Tim.BunceATig.uk>.  For other contributors see ChangeLog.

       Copyrights 1995-2000 Graham Barr <gbarrATpobox.com> and 2001-2007 Mark
       Overmeer <perlATovermeer.net>.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.  See

perl v5.8.8                       2008-04-14                  Mail::Field(3pm)