> Your case is different because of STI (so your comparisons here are
> all false because the objects are of different class). If it weren't
> for that then it's a slightly messed up situation - Active record
> thinks it has a new record but it doesn't
Doh! Didn't catch that. And when I do it without involving STI then
I get the results he's getting below. Sorry Moo!
Hrm... well down in AR::Base we have this:
# Returns true if the +comparison_object+ is the same object,
or is of the same type and has the same id.
def ==(comparison_object)
comparison_object.equal?(self) ||
(comparison_object.instance_of?(self.class) &&
comparison_object.id == id &&
!comparison_object.new_record?)
end
Which interestingly enough matches each of the conditions the parent
posted about.
I guess what this means then is if you're mucking around setting the
id's of a record and before they are saved you should call equal?
directly.
>> old = AdminUser.find(1)
=> #<AdminUser id: 1...>
>> new = AdminUser.new
=> #<AdminUser id: nil...>
>> new.id = 1
=> 1
>> old == new
=> false
>> new == old
=> true
>> old.equal?(new)
=> false
>> new.equal?(old)
=> false
> Fred
>
>> 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
-~----------~----~----~----~------~----~------~--~---
