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

NAME

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.

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

NAME

SYNOPSIS

DESCRIPTION

CONSTRUCTOR

METHODS

SUB-CLASS PACKAGE NAMES

AUTHOR

SEE ALSO

CREDITS

COPYRIGHT