Memoist
Memoist is an extraction of ActiveSupport::Memoizable.
Since June 2011 ActiveSupport::Memoizable has been deprecated.
But I love it,
and so I plan to keep it alive.
Usage
Just extend with the Memoist module
require 'memoist'
class Person
extend Memoist
def social_security
puts "execute!"
decrypt_social_security
end
memoize :social_security
end
person = Person.new
person.social_security
# execute!
# => (returns decrypt_social_security)
person.social_security
# => (returns the memoized value)
And person.social_security will only be calculated once.
Every memoized function (which initially was not accepting any arguments) has a (reload)
argument you can pass in to bypass and reset the memoization:
def some_method
Time.now
end
memoize :some_method
Calling some_method will be memoized, but calling some_method(true) will rememoize each time.
You can even memoize method that takes arguments.
class Person
def taxes_due(income)
income * 0.40
end
memoize :taxes_due
end
This will only be calculated once per value of income.
You can also memoize class methods.
class Person
class << self
extend Memoist
def with_overdue_taxes
# ...
end
memoize :with_overdue_taxes
end
end
When a sub-class overrides one of its parent's methods and you need to memoize both.
Then you can use the :identifier parameter in order to help Memoist distinguish between the two.
class Clock
extend Memoist
def now
"The time now is #{Time.now.hour} o'clock and #{Time.now.min} minutes"
end
memoize :now
end
class AccurateClock < Clock
extend Memoist
def now
"#{super} and #{Time.now.sec} seconds"
end
memoize :now, :identifier => :accurate_clock
end
Reload
Each memoized function comes with a way to flush the existing value.
person.social_security # returns the memoized value
person.social_security(true) # bypasses the memoized value and rememoizes it
This also works with a memoized method with arguments
person.taxes_due(100_000) # returns the memoized value
person.taxes_due(100_000, true) # bypasses the memoized value and rememoizes it
If you want to flush the entire memoization cache for an object
person.flush_cache # returns an array of flushed memoized methods, e.g. ["social_security", "some_method"]
Authors
Everyone who contributed to it in the rails repository.
- Joshua Peek
- Tarmo Tänav
- Jeremy Kemper
- Eugene Pimenov
- Xavier Noria
- Niels Ganser
- Carl Lerche & Yehuda Katz
- jeem
- Jay Pignata
- Damien Mathieu
- José Valim
- Matthew Rudy Jacobs
Contributing
- Fork it ( https://github.com/matthewrudy/memoist/fork )
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create new Pull Request
License
Released under the MIT License, just as Ruby on Rails is.