From: tim.pease@...
Date: 2008-08-26T01:51:56+09:00
Subject: [ANN] expiration-date 1.1.0 (Screaming Bacon)

expiration-date version 1.1.0
    by Tim Pease
    http://codeforpeople.rubyforge.org/expiration-date
    (the "Screaming Bacon" release)

== DESCRIPTION

Really simple caching by attaching an expiration date to attributes.

The ExpirationDate module adss two methods to a class -- expiring_attr and
expiring_class_attr. These two methods are used to declare attributes in the
instance and in the class, respectively, that will expire after some period of
seconds have elapsed. The attribute is re-initialized from the given block
after it has expired. This is a very simple form of caching.

== CHANGES

* 1 minor enhancement
  * added expiring class attributes

== SYNOPSIS

A simple example demonstrating how the block gets called after the expiration
time is passed.

  class A
    include ExpirationDate
    expiring_attr( :foo, 60 ) { 'foo' }
  end

  a = A.new
  a.foo                  #=> 'foo'
  a.foo = 'bar'
  a.foo                  #=> 'bar'

  sleep 61
  a.foo                  #=> 'foo'

A slightly more useful example. Here we are going to extract information from a
database every five minutes. This assumes you have the 'activesupport' and
'activerecord' gems installed.

  class MyModel < ::ActiveRecord::Base
    include ExpirationDate
    expiring_class_attr( :costly_data, 5.minutes ) {
      models = MyModel.find( :all, :conditions => ['costly query conditions'] )
      result = models.map {|m| # costly operations here}
      result
    }
  end

  MyModel.costly_data    #=> result

Attributes can be expired manually, and the time it takes them to expire can be
modified as well.

  class AgeDemo
    include ExpirationDate
    expiring_attr( :bar, 120 ) { Time.now }
  end

  demo = AgeDemo.new
  demo.bar               #=> now

  sleep 60
  demo.bar               #=> 60 seconds ago

  demo.expire_bar_now
  demo.bar               #=> now

  demo.alter_bar_age( 10 )
  demo.expire_bar_now
  demo.bar               #=> now
  sleep 11
  demo.bar               #=> now


Blessings,
TwP