App::Cache(3)

NAME
App::Cache - Easy application-level caching

SYNOPSIS
  # in your class:
  my $cache = App::Cache->new({ ttl => 60*60 });
  $cache->delete('test');
  my $data = $cache->get('test');
  my $code = $cache->get_code("code", sub { $self->calculate() });
  my $html = $cache->get_url("http://www.google.com/");
  $cache->set('test', 'one');
  $cache->set('test', { foo => 'bar' });
  my $scratch = $cache->scratch;
  $cache->clear;

DESCRIPTION
The App::Cache module lets an application cache data locally. There are a few times an application would need to cache data: when it is retrieving information from the network or when it has to complete a large calculation.

For example, the Parse::BACKPAN::Packages module downloads a file off the net and parses it, creating a data structure. Only then can it actually provide any useful information for the programmer. Parse::BACKPAN::Packages uses App::Cache to cache both the file download and data structures, providing much faster use when the data is cached.

This module stores data in the home directory of the user, in a dot directory. For example, the Parse::BACKPAN::Packages cache is actually stored underneath "~/.parse_backpan_packages/cache/". This is so that permisssions are not a problem - it is a per-user, per-application cache.

METHODS

  new
The constructor creates an App::Cache object. It takes three optional parameters:

•   ttl contains the number of seconds in which a cache entry expires. The default is 30 minutes.

      my $cache = App::Cache->new({ ttl => 30*60 });

•   application sets the application name. If you are calling new() from a class, the application is automagically set to the calling class, so you should rarely need to pass it in:

      my $cache = App::Cache->new({ application => 'Your::Module' });

•   directory sets the directory to be used for the cache. Normally this is just set for you and will be based on the application name and be created in the users home directory. Sometimes for testing, it can be useful to set this.

      my $cache = App::Cache->new({ directory => '/tmp/your/cache/dir' });

•   enabled can be set to 0 for testing, in which case you will always get cache misses:

      my $cache = App::Cache->new({ enabled => 0 });

  clear
Clears the cache:

  $cache->clear;

  delete
Deletes an entry in the cache:

  $cache->delete('test');

  get
Gets an entry from the cache. Returns undef if the entry does not exist or if it has expired:

  my $data = $cache->get('test');

  get_code
This is a convenience method. Gets an entry from the cache, but if the entry does not exist, set the entry to the value of the code reference passed:

  my $code = $cache->get_code("code", sub { $self->calculate() });

  get_url
This is a convenience method. Gets the content of a URL from the cache, but if the entry does not exist, set the entry to the content of the URL passed:

  my $html = $cache->get_url("http://www.google.com/");

  scratch
Returns a directory in the cache that the application may use for scratch files:

  my $scratch = $cache->scratch;

  set
Set an entry in the cache. Note that an entry value may be an arbitrary Perl data structure:

  $cache->set('test', 'one');
  $cache->set('test', { foo => 'bar' });

  directory
Returns the full path to the cache directory. Primarily useful for when you are writing tests that use App::Cache and want to clean up after yourself. If you are doing that you may want to explicitly set the 'application' constructor parameter to avoid later cleaning up a cache dir that was already in use.

  my $dir = $cache->directory;

AUTHOR
Leon Brocard <acme@astray.com>

COPYRIGHT
Copyright (C) 2005-7, Leon Brocard

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