Mail::Field(3)

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

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

DESCRIPTION
`Mail::Field' is a base class for packages that create and manipulate fields from Email (and MIME) headers. Each different field will have its own sub-class, defining its own interface.

This document describes the minimum interface that each sub-class should provide, and also guidlines on how the field specific interface should be defined.

CONSTRUCTOR
Mail::Field, and it's sub-classes define several methods which return new objects. These can all be termed to be constructors. The new constructor will create an object in the class which defines the field specified by the tag argument.

After creation of the object :-

If the tag argument is followed by a single string then the `parse' method will be called with this string.

If the tag argument is followed by more than one arguments then the `create' method will be called with these arguments. This constuctor takes as arguments the tag name, a `Mail::Head' object and optionally 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. This constructor takes as arguments a list of `Mail::Field' objects, which should all be of the same sub-class, and creates a new object in that same class.

This constructor is nor defined in `Mail::Field' as there is no generic way to combine the various field types. Each sub-class should define its own combine constructor, if combining is possible/allowed.

METHODS

SUB-CLASS PACKAGE NAMES
All sub-classes should be called Mail::Field::name where name is derived from the tag using these rules. Consider a tag as being made up of elements separated by '-' Convert all characters to lowercase except the first in each element, which should be uppercase. name is then created from these elements by using the first N characters from each element. N is calculated by using the formula :-

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

AUTHOR
Graham Barr.

Maintained by Mark Overmeer <mailtools@overmeer.net>

SEE ALSO
the MIME::* entry elsewhere in this documents

CREDITS
Eryq <eryq@rhine.gsfc.nasa.gov> - for all the help in defining this package so that `Mail::*' and `MIME::*' can be integrated together.

COPYRIGHT
Copyright (c) 1995-2001 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.