Question

I have a simple work schedule rails app. The jobs in the schedule will be ordered by the priority of the job. Since some jobs may change in priority, and by the same nature, order they need to be completed, i need to be able to update the priority and the priority of the rest of the table to ensure no 2 jobs share the same priority. Once the priority is updated, i want it to make that the list of priorities is continuous, in other words, the priorities are labeled 1,2,3,4,5,etc. instead of having gaps like 1,2,4,5,6,8,etc.

Can someone help me figure out the proper coding to achieve this?

This is what i currently have in my model:

class Job < ActiveRecord::Base
  include ActiveModel::Dirty
  belongs_to :customer
  has_many :job_items

  before_validation :update_priorities

  validates :priority, :uniqueness => true

  private

  def update_priorities
  if self.priority_changed?
    self.class.where("priority >= ?", self.priority).update_all("priority = priority + 1")
  else
    nil  
  end
end

The above code updates the priorities fine if its a brand new job. However, once i start to re-order the current jobs, gaps begin to appear in the sequence.

I am currently using Rails 3.2.1

Answer 1

I tried the acts_as_list provided by Veraticus, but it just wasn’t working properly for my application. After some fiddling with it, i changed my code to the following and it works just like i need it to.

  def update_priorities
if self.priority_changed?
  if self.priority < self.priority_was
    self.class.where("priority >= ?", self.priority).update_all("priority = priority + 1")
    self.class.where("priority > ?", self.priority_was).update_all("priority = priority - 1")
  else
    nil
  end
  if self.priority > self.priority_was
    self.class.where("priority <= ?", self.priority).update_all("priority = priority - 1")
    self.class.where("priority < ?", self.priority_was).update_all("priority = priority + 1")
  else
    nil
  end
end

end