Help language development. Donate to The Perl Foundation

ObjectCache cpan:ELIZABETH last updated on 2020-03-11



ObjectCache - A role to cache objects


use ObjectCache;

sub id(%h --> Int:D) {
    %h<id> or die "must have an id";

class Article does ObjectCache[&id] {
    has $.id;
    # has many more attributes

say => 42666789).WHICH;  # Article|42666789


The ObjectCache role mixes the logic of creating a proper ObjectType class and making sure that each unique ObjectType only exists once in memory, into a class.

The role takes a Callable parameterization to indicate how a unique ID should be created from the parameters given (as a hash) with the call to the new method. You can also adapt the given hash making sure any default values are properly applied. If there's already an object created with the returned ID, then no new object will be created but the one from the cache will be returned.

A class is considered to be an object type if the .WHICH method returns an object of the ObjAt class.

This is specifically important when using set operators (such as (elem), or Sets, Bags or Mixes, or any other functionality that is based on the === operator functionality, such as unique and squish.

The format of the value that is being returned by WHICH is only valid during a run of a process. So it should not be stored in any permanent medium.

Removing objects from cache

The ObjectCache role contains a private method !EVICT. If you'd like to have the ability to remove an object from the cache, you should create a method in your class that will call this method:

class Article does ObjectCache[&id] {
    method remove-from-cache() { self!EVICT }
    # more stuff

The !EVICT method returns the object that is removed from the cache, or Nil if the object was not in the cache.


Elizabeth Mattijsen [email protected]

Source can be located at: . Comments and Pull Requests are welcome.


Copyright 2020 Elizabeth Mattijsen

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.