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.IX Title "Mail::Field 3"
.TH Mail::Field 3 "2007-05-11" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
Mail::Field \- Base class for manipulation of mail header fields
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Mail::Field;
.Ve
.PP
.Vb 2
\&    $field = Mail::Field->new('Subject', 'some subject text');
\&    print $field->tag,": ",$field->stringify,"\en";
.Ve
.PP
.Vb 1
\&    $field = Mail::Field->subject('some subject text');
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`Mail::Field\*(C'\fR is a base class for packages that create and manipulate
fields from Email (and \s-1MIME\s0) headers. Each different field will have its
own sub\-class, defining its own interface.
.PP
This document describes the minimum interface that each sub-class should
provide, and also guidlines on how the field specific interface should be
defined. 
.SH "CONSTRUCTOR"
.IX Header "CONSTRUCTOR"
Mail::Field, and it's sub-classes define several methods which return
new objects. These can all be termed to be constructors.
.IP "new ( \s-1TAG\s0 [, \s-1STRING\s0 | \s-1OPTIONS\s0 ] )" 4
.IX Item "new ( TAG [, STRING | OPTIONS ] )"
The new constructor will create an object in the class which defines
the field specified by the tag argument.
.Sp
After creation of the object :\-
.Sp
If the tag argument is followed by a single string then the \f(CW\*(C`parse\*(C'\fR method
will be called with this string.
.Sp
If the tag argument is followed by more than one arguments then the \f(CW\*(C`create\*(C'\fR
method will be called with these arguments.
.IP "extract ( \s-1TAG\s0, \s-1HEAD\s0 [, \s-1INDEX\s0 ] )" 4
.IX Item "extract ( TAG, HEAD [, INDEX ] )"
This constuctor takes as arguments the tag name, a \f(CW\*(C`Mail::Head\*(C'\fR object
and optionally an index.
.Sp
If the index argument is given then \f(CW\*(C`extract\*(C'\fR will retrieve the given tag
from the \f(CW\*(C`Mail::Head\*(C'\fR object and create a new \f(CW\*(C`Mail::Field\*(C'\fR based object.
\&\fIundef\fR will be returned in the field does not exist.
.Sp
If the index argument is not given the the result depends on the context
in which \f(CW\*(C`extract\*(C'\fR is called. If called in a scalar context the result
will be as if \f(CW\*(C`extract\*(C'\fR was called with an index value of zero. If called
in an array context then all tags will be retrieved and a list of
\&\f(CW\*(C`Mail::Field\*(C'\fR objects will be returned.
.IP "combine ( \s-1FIELD_LIST\s0 )" 4
.IX Item "combine ( FIELD_LIST )"
This constructor takes as arguments a list of \f(CW\*(C`Mail::Field\*(C'\fR objects, which
should all be of the same sub\-class, and creates a new object in that same
class.
.Sp
This constructor is nor defined in \f(CW\*(C`Mail::Field\*(C'\fR 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.
.SH "METHODS"
.IX Header "METHODS"
.IP "parse" 4
.IX Item "parse"
.PD 0
.IP "set" 4
.IX Item "set"
.IP "tag" 4
.IX Item "tag"
.IP "stringify" 4
.IX Item "stringify"
.PD
.SH "SUB-CLASS PACKAGE NAMES"
.IX Header "SUB-CLASS PACKAGE NAMES"
All sub-classes should be called Mail::Field::\fIname\fR where \fIname\fR is
derived from the tag using these rules.
.IP "\(bu" 4
Consider a tag as being made up of elements separated by '\-'
.IP "\(bu" 4
Convert all characters to lowercase except the first in each element, which
should be uppercase.
.IP "\(bu" 4
\&\fIname\fR is then created from these elements by using the first
N characters from each element.
.IP "\(bu" 4
N is calculated by using the formula :\-
.Sp
.Vb 1
\&    int((7 + #elements) / #elements)
.Ve
.IP "\(bu" 4
\&\fIname\fR is then limited to a maximum of 8 characters, keeping the first 8
characters
.PP
For an example of this take a look at the definition of the 
\&\f(CW\*(C`_header_pkg_name\*(C'\fR subroutine in \f(CW\*(C`Mail::Field\*(C'\fR
.SH "AUTHOR"
.IX Header "AUTHOR"
Graham Barr.
.PP
Maintained by Mark Overmeer <mailtools@overmeer.net>
.SH "SEE ALSO"
.IX Header "SEE ALSO"
MIME::*s
.SH "CREDITS"
.IX Header "CREDITS"
Eryq <eryq@rhine.gsfc.nasa.gov> \- for all the help in defining this package
so that \f(CW\*(C`Mail::*\*(C'\fR and \f(CW\*(C`MIME::*\*(C'\fR can be integrated together.
.SH "COPYRIGHT"
.IX Header "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.