YAML::Node3pm

Usage

    use YAML;
    use YAML::Node;
    my $ynode = YAML::Node->new({}, 'ingerson.com/fruit');
    %$ynode = qw(orange orange apple red grape green);
    print Dump $ynode;

    --- !ingerson.com/fruit
    orange: orange
    apple: red
    grape: green

Overview

A generic node in YAML is similar to a plain hash, array, or scalar node in Perl except that it must also keep track of its type. The type is a URI called the YAML type tag.

YAML::Node is a class for generating and manipulating these containers. A YAML node (or ynode) is a tied hash, array or scalar. In most ways it behaves just like the plain thing. But you can assign and retrieve and YAML type tag URI to it. For the hash flavor, you can also assign the order that the keys will be retrieved in. By default a ynode will offer its keys in the same order that they were assigned.

YAML::Node has a class method call new() that will return a ynode. You pass it a regular node and an optional type tag. After that you can use it like a normal Perl node, but when you YAML::Dump it, the magical properties will be honored.

This is how you can control the sort order of hash keys during a YAML serialization. By default, YAML sorts keys alphabetically. But notice in the above example that the keys were Dumped in the same order they were assigned.

YAML::Node exports a function called ynode(). This function returns the tied object so that you can call special methods on it like ->keys().

keys() works like this:

    use YAML;
    use YAML::Node;
    %$node = qw(orange orange apple red grape green);
    $ynode = YAML::Node->new($node);
    ynode($ynode)->keys(['grape', 'apple']);
    print Dump $ynode;

produces:

    ---
    grape: green
    apple: red

It tells the ynode which keys and what order to use.

ynodes will play a very important role in how programs use YAML. They are the foundation of how a Perl class can marshall the Loading and Dumping of its objects.

The upcoming versions of YAML.pm will have much more information on this.