Question

I have an Attendance model that allows the user to enter a starting, ending and break time, each as a ruby Time object. Each attendance also has a day (ruby Date object). I want the ‘Date’ elements of the times to be the same, so I override the assignment operators like this:

def startTime= (t)
  self[:startTime] = Time.mktime(day.year, day.month, day.day, t.hour, t.min)
end
def endTime= (t)
  self[:endTime] = Time.mktime(day.year, day.month, day.day, t.hour, t.min)
end
def breakTime= (t)
  self[:breakTime] = Time.mktime(day.year, day.month, day.day, t.hour, t.min)
end

My problem is that my tests fail only when I override the breakTime= function. They all fail on calls to new, i.e. att = Attendance.new @valid_attributes, specifically at breakTime=:

undefined method `year’ for nil:NilClass

Apparently, breakTime= is getting called before the day is defined on the object, even though, startTime= and endTime= are not getting called so early. I realize this overriding is probably inelegant, but I’m pretty new to rails, so I imagine someone has made this mistake before. How should I be doing this differently?

Answer 1

Instead of overriding the attribute setters, use a before_save callback to change the attributes just before saving the model:

class Attendance < ActiveRecord::Base
  before_save :update_timestamps

  protected
  def update_timestamps
    self.start_time = Time.mktime(day.year, day.month, day.day, start_time.hour, start_time.min)
    # And similarly for the other columns
  end
end

For an overview on how callbacks work, have a look at the Active Record Validations and Callbacks guide over at guides.rubyonrails.org.