Kake > CGI-Wiki-Plugin-Locator-Grid > CGI::Wiki::Plugin::Locator::Grid

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Module Version: 0.03   Source  

NAME ^

CGI::Wiki::Plugin::Locator::Grid - A CGI::Wiki plugin to manage co-ordinate data.

DESCRIPTION ^

Access to and calculations using co-ordinate metadata supplied to a CGI::Wiki wiki when writing a node.

Note: This is read-only access. If you want to write to a node's metadata, you need to do it using the write_node method of CGI::Wiki.

We assume that the points are located on a flat, square grid with unit squares of side 1 metre.

SYNOPSIS ^

  use CGI::Wiki;
  use CGI::Wiki::Plugin::Locator::Grid;

  my $wiki = CGI::Wiki->new( ... );
  my $locator = CGI::Wiki::Plugin::Locator::Grid->new;
  $wiki->register_plugin( plugin => $locator );

  $wiki->write_node( "Jerusalem Tavern", "A good pub", $checksum,
                     { x => 531674, y => 181950 } ) or die "argh";

  # Just retrieve the co-ordinates.
  my ( $x, $y ) = $locator->coordinates( node => "Jerusalem Tavern" );

  # Find the straight-line distance between two nodes, in metres.
  my $distance = $locator->distance( from_node => "Jerusalem Tavern",
                                     to_node   => "Calthorpe Arms" );

  # Find all the things within 200 metres of a given place.
  my @others = $locator->find_within_distance( node   => "Albion",
                                               metres => 200 );

  # Maybe our wiki calls the x and y co-ordinates something else.
  my $locator = CGI::Wiki::Plugin::Locator::Grid->new(
                                                       x => "os_x",
                                                       y => "os_y",
                                                     );

METHODS ^

new
  # By default we assume that x and y co-ordinates are stored in
  # metadata called "x" and "y".
  my $locator = CGI::Wiki::Plugin::Locator::Grid->new;

  # But maybe our wiki calls the x and y co-ordinates something else.
  my $locator = CGI::Wiki::Plugin::Locator::Grid->new(
                                                       x => "os_x",
                                                       y => "os_y",
                                                     );
x_field
  my $x_field = $locator->x_field;

An accessor, returns the name of the metadata field used to store the x-coordinate.

y_field
  my $y_field = $locator->y_field;

An accessor, returns the name of the metadata field used to store the y-coordinate.

coordinates
  my ($x, $y) = $locator->coordinates( node => "Jerusalem Tavern" );

Returns the x and y co-ordinates stored as metadata last time the node was written.

distance
  # Find the straight-line distance between two nodes, in metres.
  my $distance = $locator->distance( from_node => "Jerusalem Tavern",
                                     to_node   => "Calthorpe Arms" );

  # Or in kilometres, and between a node and a point.
  my $distance = $locator->distance( from_x  => 531467,
                                     from_y  => 183246,
                                     to_node => "Duke of Cambridge",
                                     unit    => "kilometres" );

Defaults to metres if unit is not supplied or is not recognised. Recognised units at the moment: metres, kilometres.

Returns undef if one of the endpoints does not exist, or does not have both co-ordinates defined. The node specification of an endpoint overrides the x/y co-ords if both specified (but don't do that).

Note: Works to the nearest metre. Well, actually, calls int and rounds down, but if anyone cares about that they can send a patch.

find_within_distance
  # Find all the things within 200 metres of a given place.
  my @others = $locator->find_within_distance( node   => "Albion",
                                               metres => 200 );

  # Or within 200 metres of a given location.
  my @things = $locator->find_within_distance( x      => 530774,
                                               y      => 182260,
                                               metres => 200 );

Units currently understood: metres, kilometres. If both node and x/y are supplied then node takes precedence. Croaks if insufficient start point data supplied.

SEE ALSO ^

AUTHOR ^

Kake Pugh (kake@earth.li).

COPYRIGHT ^

     Copyright (C) 2004 Kake L Pugh.  All Rights Reserved.

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

CREDITS ^

This module is based heavily on (and is the replacement for) CGI::Wiki::Plugin::Locator::UK.

The following thanks are due to people who helped with CGI::Wiki::Plugin::Locator::UK: Nicholas Clark found a very silly bug in a pre-release version, oops :) Stephen White got me thinking in the right way to implement find_within_distance. Marcel Gruenauer helped me make find_within_distance work properly with postgres.

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