[Pyobjc-dev] Some PyObC tweaks for using EOF and custom frameworks

[Pierce T. W. I. <pi...@ma...>]

  Background:

   I'm using EOF 4.5, and I wanted to be able to use python to write  
test scripts, mini programs, and scripts that interacted with both our  
object model, and shell tools.

  Every thing works ok, except I had to make some tweaks.

  1. I have to touch NSCalendarDate after loading Foundation and before  
loading any other frameworks via loadBundle. I think this causes  
+initialize for the various Foundation classes early on, which probably  
should have been done by the "import Foundation" step originally, but  
that might be tough. I'm using NSCalendarDate because NSCalendarDate  
had a +initialize method that was deadlocking, but using it seemed to  
fix everything.

  Doing this after the loadBundle call caused problems with both  
Foundation and the loaded frameworks.

i.e I have to do some VOODOO:

import objc
import Foundation

#VOODOO
from Foundation import NSCalendarDate
NSCalendarDate.date().description()

objc.loadBundle("EOAccess",globals(),bundle_path="/System/Library/ 
Frameworks/EOAccess.framework")


  2. EOF does some hackery on the ObjC where objects that haven't yet  
been fetched from the database have a fake "isa" pointer. When the  
object gets fetched, the isa pointer get reset to that of the real  
class.

   This crashes on the Python side, but it works if you pre resolve the  
fault on the ObjC side.

That is in Python:

mystock= trade.stock()

bus errors, but

  mystock= trade.valueForKeyPath_("stock.self")

works.

  Given this, the fix is easy.

  In objc_support.m:pythonify_c_value we have:

	case _C_ID:
	{
		id obj = *(id *) datum;
		if (obj == nil) {

Which becomes:

	case _C_ID:
	{
		id obj = *(id *) datum;
		obj=[obj self];

		if (obj == nil) {

  This forces the fault to resolve on the Objective-C side before python  
creates the python object. Then:

mystock= trade.stock()

  Will work. I'm not sure what would happen if an object got  
invalidated. It seems in that case, you'd want to call [obj self]  
before doing any method calls on it, but I wasn't sure where to put  
that.

  Pierce