foodsoft/app/models/periodic_task_group.rb

class PeriodicTaskGroup < ActiveRecord::Base
  has_many :tasks, dependent: :destroy

  PeriodDays = 7
  
  def has_next_task?
    return false if tasks.empty?
    return false if tasks.first.due_date.nil?
    return true
  end

  def create_next_task
    template_task = tasks.first
    self.next_task_date ||= template_task.due_date + PeriodDays
    
    next_task = template_task.dup
    next_task.due_date = next_task_date    
    next_task.save

    self.next_task_date += PeriodDays
    self.save
  end

  def exclude_tasks_before(task)
    tasks.where("due_date < '#{task.due_date}'").each do |t|
      t.update_attribute(:periodic_task_group, nil)
    end
  end
end