> Hi Fred, > > Thank you for the response! What you said made sense. thanks for the > explanation. > > However, looking at the last criteria of the == implementation, we can > see why something like what i mentioned would fail: > > let's say i have an 2 AR objects: >> old = Something.find(1) > => #<Something id: 1> > > then i create a new object: >> new = Something.new > => #<Something id: nil> >> new.id = 1 # something like this is possible, how or why is another >> story... >> new > => #<Something id: 1> > > now do: >> new == old > => true >> old == new > => false > > == method should be commutative, right?
You've got something screwy somewhere... old = Toy.fin>> old = Toy.find(1) => #<BabyToy id: 1, ......> >> new = Toy.new => #<Toy id: nil, ....> >> new.id = 1 => 1 >> old == new => false >> new == old => false Rails 2.3.2.1 -philip > appreciate any comments! > -Moo > > On Apr 10, 10:52 am, Frederick Cheung <frederick.che...@gmail.com> > wrote: >> On Apr 10, 5:50 pm, Moo <janec...@gmail.com> wrote:> Anyone has any >> thoughts on this please? >> >> Basically the rationale is that == should mean 'do these objects >> correspond to the same database row ?' >> >> The reason why unsaved records are special cased is that two unsaved >> record would have equal id (nil in both cases) but if you saved them >> you would end up with 2 distinct rows in your database. >> >> I'm not sure why you're getting new ==old not being the same as old >> == new. They should both be false (and are on my machine) >> >> Fred >> >>> On Apr 8, 5:29 pm, Moo <janec...@gmail.com> wrote: >> >>>> Hi Everyone, >> >>>> I'm running into a problem with theActiveRecord::Base "==" method >>>> defined here (it's 2.3.2, but it looks the same in older versions >>>> too): >> >>>> # File rails-2.3.2/activerecord/lib/active_record/base.rb, >>>> line >>>> 2816 >>>> 2816: def ==(comparison_object) >>>> 2817: comparison_object.equal?(self) || >>>> 2818: (comparison_object.instance_of?(self.class) && >>>> 2819: comparison_object.id == id && >>>> 2820: !comparison_object.new_record?) >>>> 2821: end >> >>>> Because of the last criteria (!comparison_object.new_record?), >>>> something like this happens... say i have a new record and an >>>> existing >>>> record (different objects) and compare them: >> >>>>> new == old >>>> => true >>>>> old == new >> >>>> => false >> >>>> If this is intentional, can someone please explain why this is? >> >>>> Also what is the rational of only comparing the ID and not the >>>> all the >>>> values too and why does it matter if it's a new record or not? >> >>>> Thank you! >>>> -Moo > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
