[Pyobjc-dev] NSString & mutability

[Just v. R. <ju...@le...>]

Someone on comp.sys.mac.programmer.help suggested a trick to find out
whether an NS[CF]String is mutable or not: by comparing classForCoder to
NSString. Nifty.

This allowed me to patch objc_support.m so it only converts immutable
strings to Python strings:

Index: objc_support.m
===================================================================
RCS file: /cvsroot/pyobjc/pyobjc/Modules/objc/objc_support.m,v
retrieving revision 1.20
diff -c -r1.20 objc_support.m
*** objc_support.m  31 Jan 2003 10:35:29 -0000  1.20
--- objc_support.m  4 Feb 2003 20:11:36 -0000
***************
*** 614,620 ****
            retobject = [(OC_PythonDictionary *)obj pyObject];
            Py_INCREF(retobject);
          }
!         else if ([obj isKindOfClass:[NSString class]])
          {
            /* All string classes seem to be subclasses of NSString.
            * We convert to a python string where possible, and a python
--- 614,621 ----
            retobject = [(OC_PythonDictionary *)obj pyObject];
            Py_INCREF(retobject);
          }
!         else if ([obj isKindOfClass:[NSString class]] &&
!                  [obj classForCoder] == [NSString class])
          {
            /* All string classes seem to be subclasses of NSString.
            * We convert to a python string where possible, and a python


This works nicely:

  >>> from Foundation import *
  >>> x = NSMutableString.stringWithString_("asdasd")
  >>> x
  <NSCFString objective-c instance 0x430840>
  >>> x.appendString_("aaa")
  >>> repr(x)
  '<NSCFString objective-c instance 0x430840>'

However, str() fails:

  >>> str(x)
  Traceback (most recent call last):
    File "<stdin>", line 1, in ?
  TypeError: __str__ returned non-string (type NSCFString)
  >>> 

I can't seem to find where I can repair this.

Bill, this is not to say I'm _completely_ opposed to wrapping instead of
converting strings, but more that I'd like to see how "partial
conversion" (ie. don't convert if the string is mutable) works in
practice.

Just