Question

Is there a way to get a PyObjC proxy object for an Objective-C object, given only its id as an integer? Can it be done without an extension module?

In my case, I’m trying to get a Cocoa proxy object from the return value of wx.Frame.GetHandle (using wxMac with Cocoa).

Answer 1

The one solution I did find relies on ctypes to create an objc_object object from the id:

import ctypes, objc
_objc = ctypes.PyDLL(objc._objc.__file__)

# PyObject *PyObjCObject_New(id objc_object, int flags, int retain)
_objc.PyObjCObject_New.restype = ctypes.py_object
_objc.PyObjCObject_New.argtypes = [ctypes.c_void_p, ctypes.c_int, ctypes.c_int]

def objc_object(id):
    return _objc.PyObjCObject_New(id, 0, 1)

An example of its use to print a wx.Frame:

import wx

class Frame(wx.Frame):
    def __init__(self, title):
        wx.Frame.__init__(self, None, title=title, pos=(150,150), size=(350,200))

        m_print = wx.Button(self, label="Print")
        m_print.Bind(wx.EVT_BUTTON, self.OnPrint)

    def OnPrint(self, event):
        topobj = objc_object(top.GetHandle())
        topobj.print_(None)

app = wx.App()
top = Frame(title="ObjC Test")
top.Show()

app.MainLoop()

It’s a little nasty since it uses ctypes. If there’s a pyobjc API function I overlooked or some other neater way to do it, I’d surely be interested.