Dynamic changes to schedule.rb for Whenever gem

schedule.rb

require File.expand_path('../config/environment', __FILE__)

upload_interval = Setting.for('FTP Update Interval').value || 15
every upload_interval.to_i.minutes do
  runner 'Device.upload_csv_to_ftp'
end

Setting.rb

class Setting < ActiveRecord::Base

  validates_uniqueness_of :var
  validates_presence_of :value

  after_save :send_cron_later

  #Setting.for(:display).set=(value)
  def self.for(var)
    find_or_create_by_var(var)
  end

  def set=(value)
     update_attributes(:value => value)
  end

  def send_cron_later
    #Using delayed job to run this later to not hold up an HTTP thread.
    delay.update_cron if var.eql?("FTP Update Interval")
  end

  def update_cron
    system 'bundle exec whenever --update-crontab store'
  end
end