[python-win32] Input-only vs. In/Out Function Parameters

[Smith, Brian (CR)]

Hi,
 
Just thought I'd bump this to see if I could get a response...
 
Brian
 
>
> I am new to COM programming and have a question about function 
> parameters when implementing a COM object in Python. 
> 
> After reading "Python Programming on Win32", I have managed to create a 
> working COM object, where "working" is defined as "I can use it from 
> Excel VBA". 
> 
> I have a function like this: 
> 
> def func(self, in1, inout1, in2, inout2) 
> 
> where the in* parameters are input only and inout* are input and output. 
> At the end of the function I return an error code and new values for the 
> in/out parameters. I.e.: 
> 
> return( errorCode, new_inout1, new_inout2 ) 
> 
> This seems to work fine if it is called from VBA as 
> 
>     errorCode = object.func( CONSTANT_1, var1, CONSTANT_2, var2 ) 
> 
> or 
> 
>     errorCode = object.func( 42, var1, 7.4, var2 ) 
> 
> but it breaks if the VB program does this: 
> 
>     c1 = CONSTANT_1  ' c1 is a previously declared variable 
>     c2 = 7.4         ' c2 is a previously declared variable 
>     errorCode = object.func( c1, var1, c2, var2 ) 
> 
> because c1 will then be assigned new_inout1 and var1 will be assigned 
> new_inout2, while c2 and var2 will not be assigned anything. 
> 
> Short of telling the VB programmer "Don't do that", how do I prevent 
> this problem? 
> 
> Thanks, 
> Brian 

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