RoadToElDuration

Like a counter cache but for length in time attributes.

If the duration or length in time of an object needs to be calculated from the duration or length in time of associated records this gem helps you achieve that easily.

It handles automatic recalculations as child records are added, removed, and transferred to other parent records.

It also comes with its own coder class that handles serializing and deserializing the duration columns to and from instances of the ActiveSupport::Duration class and the Ruby Integer class. This is an opt-in feature so you don't have to use it if you don't want.

The gem provides two modules that you can include in your models. One named RoadToElDuration::Calculations which provides the calculates_duration_from and updates_duration_of methods and the other named RoadToElDuration::Coder which provides the coder class that is used to serialize and deserialize the duration columns.

Let's look at a simple example.

class Episode < ApplicationRecord
  include RoadToElDuration::Calculations

  belongs_to :series

  serialize :duration, coder: RoadToElDuration::DurationCoder
  updates_duration_of :series
end


class Series < ApplicationRecord
  include RoadToElDuration::Calculations

  has_many :episodes

  serialize :duration, coder: RoadToElDuration::DurationCoder
  calculates_duration_from :episodes
end

Here we have two models, Episode and Series. The Series model has its duration column serialized with the RoadToElDuration::DurationCoder coder and the Episode model has its duration column serialized with the RoadToElDuration::DurationCoder coder as well.

The Series model also has its duration attribute populated from the sum of episode duration that belongs to a series.

This setup assumes that both the Episode and Series models have an integer column on their tables named duration that is used to store the duration in seconds.

If your columns are named differently you can specify the column names in both the calculates_duration_from and updates_duration_of methods by passing the column name as a symbol or a string as the column keyword argument.

For example:

class Episode < ApplicationRecord
  include RoadToElDuration::Calculations

  belongs_to :series

  serialize :duration, coder: RoadToElDuration::DurationCoder
  updates_duration_of :series, column: :total_length
end


class Series < ApplicationRecord
  include RoadToElDuration::Calculations

  has_many :episodes

  serialize :duration, coder: RoadToElDuration::DurationCoder
  calculates_duration_from :episodes, column: :length
end

Add this line to your application's Gemfile:

gem "road_to_el_duration"

And then execute:

$ bundle

If you would like to contribute something, go for it. 👍

The gem is available as open source under the terms of the MIT License.