Loading part of a has_many association, and sorting as I add more elements

rubyonrails-talk
1

Hello,

I have what boils down to a timesheet app. Before I display the entry form (eg one text input per day in the current schedule) I load the shifts I have in the database for the given period, then create new, blank shifts to fill in the blanks for the week before sorting the shifts by date and assigning to the relation.

This works in that if I have 2 shifts stored in the DB and want to display a week, the routine adds 5 more blank shifts and sorts. However, once I assign this to the relationship, the sorting seems to revert to created_by rather than the sort order of the array I assigned (example below)

class Shift < ActiveRecord::Base   belongs_to :employee end

class Employee < ActiveRecord::Base      has_many :shifts, :order => "date ASC"

     def load_schedule(start, numdays)

        raise "numdays must be >=1" if numdays < 1         # find the shifts that are already stored that are between start and start+numdays         currentshifts = Shift.find(            :all,            :conditions => ["employee_id = :eid AND date >= :start AND date <= :finish",            { :eid => self.id,               :start => start.at_beginning_of_day,               :finish => start.at_beginning_of_day +numdays.days-1.second            } ] )

         newshifts = Array.new          # iterate through the week and create new shifts for the days that are missing          # code omitted

         # debugging stuff          puts "============================================"          c = newshifts.to_a + currentshifts.to_a          puts "unsorted"          c.each { |s| puts "#{s.date} - #{s.hours}" }          d = c.sort_by { |a| a.date }          puts "sorted"          d.each { |s| puts "#{s.date} - #{s.hours}" }          self.shifts = d          puts "in employee object"          self.shifts.each { |s| puts "#{s.date} - #{s.hours}" } end

The results of this are: .============================================ unsorted 2009-02-25 - 2009-02-26 - 2009-02-28 - 2009-03-02 - 2009-03-03 - 2009-02-27 - 1.5 2009-03-01 - 1.5 sorted 2009-02-25 - 2009-02-26 - 2009-02-27 - 1.5 2009-02-28 - 2009-03-01 - 1.5 2009-03-02 - 2009-03-03 - in employee object 2009-02-27 - 1.5 2009-03-01 - 1.5 2009-02-25 - 2009-02-26 - 2009-02-28 - 2009-03-02 - 2009-03-03 -

The reason I'm sorting and adding the blank shifts in the model is because I'm passing the object back up to the view where I'm using the FormHelpers to create the form. I'm loading a subset of the shifts at a time because it seems wasteful to load a year's worth of timesheet data if I'm only working with a week.

Why/how is the Array getting resorted when I assign it to the association? How do I stop it? Should I be working with a subset of the shift data this way, or is there a better way? Am I going about this completely wrong?

Thanks,

Sean

2

Why/how is the Array getting resorted when I assign it to the association? How do I stop it?

The key bit is the replace method in

It's trying to minimise the number of delete or updates to the database, so it first removes all the records that should no longer be there, then appends all the records that need to be added to the collection, which will mess with your order if the collection is non empty to begin with

If you reload the association the records should come out in the right order

Fred

3

self.shifts = (newshifts.to_a + currentshifts.to_a).sort_by { |a| a.date }    # Reload to get them in order    self.shifts.reload

That seems to work (or at least passes my test cases :wink: ), thanks a lot!

Sean