Re: Mk4py - Strange Behaviour when assigning views

You problem is pretty simple, the storage you are declaring in
make_view is being de-allocated when it goes out of scope.

Move st=make.storage() to the top level as in

import metakit.metakit as mk
st = make.storage()

That should fix the problem.
Brian

On Sun, 19 Sep 2004 09:24:26 -0400, choppystride <[email protected]> wrote:
> Hi,
> 
> Please look at the following code:
> 
> import metakit.metakit as mk
> 
> def make_view ():
>         st = mk.storage()
>         vw = st.getas( "test[val:I]" )
> 
>         for i in xrange(3): vw.append( val=i )
> 
>         print 'inside make_view():'
>         print '   view obj: ', vw
>         print '   structure: ', vw.structure()
>         for row in vw: print '   row.val= ', row.val
>         return vw
> 
> def test1 ():
>         v2 = make_view()
>         print 'outside make_view()'
>         print '   view obj: ', v2
>         print '   structure: ', v2.structure()
>         for row in v2: print '   row.val= ', row.val
> 
> if __name__ == '__main__':
>         print 'metakit version ', mk.version
>         test1()
> 
> When running the code, I got the following output & error:
> 
> metakit version  2.4.9.3
> inside make_view():
>    view obj:  <PyView object at 8f95c0>
>    structure:  [Property('I', 'val')]
>    row.val=  0
>    row.val=  1
>    row.val=  2
> outside make_view()
>    view obj:  <PyView object at 8f95c0>
>    structure:  []
>    row.val=
> Traceback (most recent call last):
>   File "test2.py", line 48, in ?
>     test1()
>   File "test2.py", line 21, in test1
>     for row in v2: print '   row.val= ', row.val
> AttributeError: val
> 
> A similar problem occurs when I store the view as an instance var in
> an object and then access it later:
> 
> class testmk ( object ):
>         def __init__ ( self ):
>                 st = mk.storage()
>                 self.vw = st.getas( "test[val:I]" )
>                 for i in xrange(3): self.vw.append( val=i )
> 
>         def prtvw ( self ):
>                 print 'tmk view obj: ', self.vw
>                 print 'tmk: structure: ', self.vw.structure()
>                 for row in self.vw: print 'tmk: row.val= ', row.val
> 
> def test_obj ():
>         tmk = testmk()
>         tmk.prtvw()
> 
> if __name__ == '__main__':
>         print 'metakit version ', mk.version
>         test_obj()
> 
> The resulting output and error are:
> 
> metakit version  2.4.9.3
> tmk view obj:  <PyView object at 8df7d0>
> tmk: structure:  []
> tmk: row.val=
> Traceback (most recent call last):
>   File "test2.py", line 69, in ?
>     test_obj()
>   File "test2.py", line 65, in test_obj
>     tmk.prtvw()
>   File "test2.py", line 61, in prtvw
>     for row in self.vw: print 'tmk: row.val= ', row.val
> AttributeError: val
> 
> I can circumvent this problem by manipulating the storage object
> instead. Then whenever I need the view, I can just call
> storage.view(...).  This seems to be OK.
> 
> Am I doing something wrong or could there be a possible bug?
> 
> I'm using Active Python v2.3.2 on Win XP.
> 
> Thanks!
> 
> --
> Cheers,
> choppystride
> 
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