"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.
new ( TAG [, STRING | OPTIONS ] )
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.
extract ( TAG, HEAD [, INDEX ] )
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.
combine ( FIELD_LIST )
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
parse
set
tag
stringify
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"
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) 2002-2003 Mark Overmeer, 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.
