[Pyobjc-dev] another odd problem

[Steven D. A. <st...@ne...>]

Thanks to Ronald and Martina for their comments regarding the non-retained
objects that acted as datasources for an NSComboBox.  Setting those objects
as instance variables in the controller object did indeed solve that
problem.  However, I have encountered another weird problem which seems like
a possible bug.

Essentially, it seems classes that inherit from Foundation.NSObject do not
correctly see methods in superclasses before the one that inherited from
NSObject.  However, note that dir does show the attribute!  Consider the
following code snippet:

    import Foundation
    class ListManager:
        def init( self ):
            return self
        def key_for_index( self, index ):
            print "INDEX = ", index
    
    class foo( Foundation.NSObject, ListManager ):
        def init( self ):
            ListManager.init( self )
            return self
    
    i = foo.alloc().init()
    if 'key_for_index' in dir( i ):
        present = "is"
    else:
        present = "is not"
    
    print "dir shows that key_for_index %s an attribute of i" % present
    i.key_for_index( 5 )

If you run this code, you get the following:

    >>> print "dir shows that key_for_index %s an attribute of i" % present
    dir shows that key_for_index is an attribute of i
    >>> i.key_for_index( 5 )
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    AttributeError: 'foo' object has no attribute 'key_for_index'


However, if you modify the code to avoid inheriting from
Foundation.NSObject, you get the expected behavior:

    import Foundation
    class ListManager:
        def init( self ):
            return self
        def key_for_index( self, index ):
            print "INDEX = ", index
    
    class foo( ListManager ):
        def init( self ):
            ListManager.init( self )
            return self
    
    i = foo()
    if 'key_for_index' in dir( i ):
        present = "is"
    else:
        present = "is not"
    
    print "dir shows that key_for_index %s an attribute of i" % present
    i.key_for_index( 5 )

The result:

    >>> print "dir shows that key_for_index %s an attribute of i" % present
    dir shows that key_for_index is an attribute of i
    >>> i.key_for_index( 5 )
    INDEX =  5


[...] After playing around with this awhile, I moved Foundation.NSObject to
the ListManager class and now it seems to work.  But is it a bug that the
code in the first example above fails to work?

-- 
Steven D. Arnold                             st...@ne...
     "One has a moral responsibility to disobey unjust laws."
                        Martin Luther King
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