Using a duration field in a Rails model

Question

I\'m looking for the best way to use a duration field in a Rails model. I would like the format to be HH:MM:SS (ex: 01:30:23). The database in use is sqlite locally and Postgr

Answer 1

In Rails 5, you can use ActiveRecord::Attributes to store ActiveSupport::Durations as ISO8601 strings. The advantage of using ActiveSupport::Duration over integers is that you can use them for date/time calculations right out of the box. You can do things like Time.now + 1.month and it's always correct.

Here's how:

Add config/initializers/duration_type.rb

class DurationType < ActiveRecord::Type::String
  def cast(value)
    return value if value.blank? || value.is_a?(ActiveSupport::Duration)

    ActiveSupport::Duration.parse(value)
  end

  def serialize(duration)
    duration ? duration.iso8601 : nil
  end
end

ActiveRecord::Type.register(:duration, DurationType)

Migration

create_table :somethings do |t|
  t.string :duration
end

Model

class Something < ApplicationRecord
  attribute :duration, :duration
end

Usage

something = Something.new
something.duration = 1.year    # 1 year
something.duration = nil
something.duration = "P2M3D"   # 2 months, 3 days (ISO8601 string)
Time.now + something.duration  # calculation is always correct