Comparing identical DateTime objects in ruby — why are these two DateTime.now's not equal?

Question

In a rails app, I have model code of the form:

def do_stuff(resource)
  models = Model.where(resource: resource)
  operated_at = DateTime.now

  models.each         


        

Answer 1

Possible clue; the act of saving and reloading truncates the seconds_fraction part of the DateTime. The date field becomes an instance of ActiveSupport::TimeWithZone. Just saving without reloading doesn't do this; the real DateTime object is still there.

2.0.0-p195 :001 > dt            =  DateTest.create
2.0.0-p195 :002 > right_now     =  DateTime.now
2.0.0-p195 :004 > dt.created_at =  right_now
2.0.0-p195 :005 > dt.created_at == right_now
 => true 

2.0.0-p195 :006 > dt.save
2.0.0-p195 :007 > dt.created_at == right_now
 => true 

2.0.0-p195 :008 > dt = DateTest.find(dt.id)
2.0.0-p195 :009 > dt.created_at == right_now
 => false 

Edit: of course calling models.each is going to load the models there and then because of the lazy loading behaviour. Props to the other answerer. As an experiment, try setting models to Model.where(resource: resource).to_a.