TimeHash

https://rubygems.org/gems/time-hash

Just a normal Ruby Hash, with time (seconds) based expiration. (It's pretty scary and makes Haskell programmers cry.)

API-wise, the only changes are that []= is no longer used, and in it's place you use put, which takes a key, value, and a time-to-live (seconds).

Also added: expired?(key) and expire! (explained below).

Usage:

gem install time-hash

require 'time-hash'

th = TimeHash.new
th.put(:key, 1234, 10) # this will exist for 10 seconds
th.put(:key2, 12345, 0.2) # this will exist for 0.2 seconds
th # => { key: 1234, key2: 12345} }
 # after 0.2 seconds
th.has_key?(:key2) # => false
th # => { key: 1234 }
 # after 10 seconds
th # => {}

th[1] = 3 # this will raise an error. You must have a time! (use put)

This assumes that you want automatic expiration to occur. If not...

require 'time-hash'

th = TimeHash.new(false)
th.put(:key, 1234, 0.001)
 # after 0.001 seconds
th # => { key: 1234 } # because it doesn't automatically expire
th.expire!
th # => {}

This means before any hash you must call expire! to remove out-of-date items.

About

It just wraps a normal hash and keeps track of another hash, times, which is key => [time added, ttl]. You can examine this read-only field using th.times.

Unfortunately this class adds O(n) to all operations (even simple ones) if you have automatic expiration on. But it's not too big of a deal, and if your hash gets big just manually expire things.