[Nitro] The has_one/belongs_to relationship

Jonathan Buch john at oxyliquit.de
Mon Aug 20 06:52:08 EDT 2007


Hi,

> Well, my issue is that I need my Account object to reference my Character
> object and my Character object to refer back to that same Account object. I
> assumed that the relationship would work like this:
>load Account
> load Account#character_oid
> Account <-> Character
>But, it's doing this, I think:
> load Account
> load Account#character
> load Character#account
> Account -> Character -> Account (different instance)

>>> a1 = Account.new
>>> a1.character = Character.create self
>>> a1.equal?(a1.character.account) #=> false

This sums it up I guess, you call a1.character.account so it is
"Account[25] -> Character[17] -> Account[25]".  Where the first and last
are the 'same' object, but not identical.

The identify of objects is (imo) mostly irrelevant and hard to 'get to'
anyway.  When Og wanted to keep the identity for identical (meaning same
primary key) elements, it'd really have to jump through hoops.  It has
several other problems then too, like having to keep track of every single
loaded element (this 'cache' has to be cleaned, when?), making Og non-thread-
safe (you always work on the identical copy, if you change it in one thread
it gets changed for all), and the implementation would just be so complex and
would make Og even slower.

Og theoretically would be able to save the Account in the Character right
after saving (which I asked George about) which would then point to the
identical object as the Account.

> Is this how it works then, or did I perhaps implement something incorrectly?
> Since it's just a one_on_one relationship, I can always reference the Account
> myself in the Character class, but I was trying to be Ogish and have it load
> and attach itself. However, it's essential that the created objects reference
> eachother -- do I need to do the loading myself then
> (Character.find_by_account_oid(Account#oid), where Character#account_oid is a
> field created and set by me)?

Well, why would you want to do that by yourself, if Og does it already?  When
you load it yourself, the object_id you will get will differ in the exact
same way.

But, to answer your question:  yes, that's how it works.

a1 = Account.create
c1 = Character.create
a1.character = c1
a1.save
c1.blah # do other stuff

I do this, so if I need the same character in the same scope again, I just
make it to a local variable, that is imo nicer to read, makes shorter code
and even is more efficient.

> However, it's essential that the created objects reference eachother

They do, just not to the object with the same object_id, is that really
a problem?

>> Og overrides ==() to react on the primary key of that model.
>>
>Oh, this probably explains some unexpected results from Array#delete(self) in
> my Character class -- I assumed it was Og-related, but good to know for sure
> and why.

Glad it cleared some things up.  :)

Jo

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