awakeFromNib and File's Owner

FROM : Mark Trombino
DATE : Mon Dec 13 19:45:46 2004

Hello,

I'm porting an old NEXSTEP app I wrote to OS X and in the process I'm
cleaning up some problems that the app has always had.  One of the
problems turned out to have been because awakeFromNib is getting sent
twice to the same object.  This object is instantiated in a nib file,
and then later loads other nib files as the File's Owner.  I've done
some searching on this and other forums and have discovered that this
is correct behavior, but I don't understand why...

In my mind, an object should only be sent awakeFromNib once and only
when the object is instantiated in a nib file. I've always considered
the File's Owner to be external to the nib file, since it is the object
that is loading that file or at least already part of the application. 
  There seems to be no good reason why it should be sent an awakeFromNib
since it is already part of the app.  Even if the File's Owner isn't
the object loading the code, but instead a different object, it would
seem that it still is already part of the app and is already "awake".

When I encounter a problem like this I usually discover that there are
really good  reasons why it is the way it is.  I'm more curious than
anything to find out why having the File's Owner sent an awakeFromNib
is the right thing to do.  Can anyone explain that to me?  I obviously
have the wrong idea of what awakeFromNib is for!

Possible workarounds include moving the code out of awakeFromNib and
into an init method.  However, I need to make sure all objects have
been instantiated before doing some of the things I'm doing in
awakeFromNib.  That's why the code was there in the first place.  A
second workaround is to use a flag to see if awakeFromNib has already
been executed.  A third might be to  wait for a
NSBundleDidLoadNotification, check to see what classes were loaded, and
do the appropriate thing.  Are there any other solutions?

Incidentally, this behavior existed even back in NEXTSTEP days.

Thanks!

Mark