[C++-sig] Re: Boost.Python not resolving overloads

[Niall Douglas]

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On 20 Sep 2003 at 21:46, David Abrahams wrote:

> >>>> from TnFOX import *
> >>>> fh=FXFile("fred.txt")
> >>>> print fh.name()
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in ?
> > Boost.Python.ArgumentError: Python argument types in
> >     FXFile.name()
> > did not match C++ signature:
> >     name(class FX::FXString)
> >     name(class FX::FXFile {lvalue})
> >>>> print fh.name(fh)
> > fred.txt
> >
> > As it says, there are two name()'s defined. 
> 
> Clearly it's a static method which takes a single argument.  if you
> want to call it as fh.name() you can't make it static (or you need an
> overload which takes no arguments).

Yes sorry - it's 3am here. One of the name()'s is static but the 
other one isn't:

class FXFile
{
   const FXString &name() const;
   static FXString name(const FXString &file);
};

Now in my example above, I was calling name(void), not name(file). If 
you call name(fh) then it correctly calls the name(void).

> > I tried a number of other 
> > functions with no parameters and all of them cause an error if there
> > are overloads present. The only way to make them work is to include
> > the instance as the first parameter.
> >
> > Is this right? It's counter-intuitive and inconvenient - surely
> > boost.python can try inserting the instance if no parameters are
> > present?
> 
> Wha???  No, it can't just guess at what you mean.  

I don't see why. If one of my name()'s is zero parameters and the 
other one takes a string, and I call name(), then it's obvious I want 
the zero parameter one.

Besides, the error message is from Boost.Python, not Python.

If this is not known behaviour, I'll make you a demo though it would 
be trivial for you to write yourself.

Cheers,
Niall





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