man Graph::Writer (3): base class for Graph file format writers

SYNOPSIS

package Graph::Writer::MyFormat;
use Graph::Writer;
use vars qw(@ISA);
@ISA = qw(Graph::Writer);
sub _write_graph
{
my ($self, $graph, $FILE) = @_;
# write $graph to $FILE
}

DESCRIPTION

Graph::Writer is a base class for Graph file format writers. A particular subclass of Graph::Writer will handle a specific file format, and generate a Graph, represented using Jarkko Hietaniemi's Graph class.

You should never create an instance of this class yourself, it is only meant for subclassing. If you try to create an instance of Graph::Writer, the constructor will throw an exception.

METHODS

new()

Constructor - generate a new writer instance. This is a virtual method, or whatever the correct lingo is. You're not meant to call this on the base class, it is inherited by the subclasses. Ie if you do something like:

  $writer = Graph::Writer->new();

It will throw an exception.

write_graph()

Read a graph from the specified file:

  $graph = $writer->write_graph($file);

The $file argument can either be a filename, or a filehandle for a previously opened file.

SUBCLASSING

To create your own graph format writer, create a module which subclasses Graph::Writer. For example, suppose DGF is a directed graph format - create a Graph::Writer::DGF module, with the following structure:

  package Graph::Writer::DGF;
  use Graph::Writer;
  use vars qw(@ISA);
  @ISA = qw(Graph::Writer);
  sub _write_graph
  {
    my $self  = shift;
    my $graph = shift;
    my $FILE  = shift;
    while (<$FILE>)
    {
    }
    return 1;
  }
  1;

Note the leading underscore on the _write_graph() method. The base class provides the public method, and invokes the private method which you're expected to provide, as above.

If you want to perform additional initialisation at construction time, you can provide an _init() method, which will be invoked by the base class's constructor. You should invoke the superclass's initialiser as well, as follows:

  sub _init
  {
    my $self = shift;
    $self->SUPER::_init();
    # your initialisation here
  }

Someone can then use your class as follows:

  use Graph::Writer::DGF;
  $writer = Graph::Writer::DGF->new();
  $writer->write_graph($graph, 'foo.dgf');

REPOSITORY

<https://github.com/neilb/Graph-ReadWrite>

AUTHOR

Neil Bowers <[email protected]>

COPYRIGHT

This script is free software; you can redistribute it and/or modify it under the same terms as Perl itself.