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List:       kde-devel
Subject:    Re: Problem with derived class function name the same as base class
From:       Stephen Allewell <stephen () mirramar ! fsnet ! co ! uk>
Date:       2002-06-29 21:18:18
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Malte Starostik wrote:
> Am Saturday 29 June 2002 22:41 schrieb Stephen Allewell:
> > I have a class 'Editor' that is derived from QScrollView.  QScrollView
> > has the function
> > QPoint contentsToViewport(const QPoint &p)  to convert content
> > coordinates to viewport coordinates.
> > I also require to convert a QRect so I wrote the function:
> >
> > QRect Editor::contentsToViewport(QRect &r) {
> >   return
> > QRect(contentsToViewport(r.topLeft()),contentsToViewport(r.bottomRight()));
> > }
> >
> > but when compiling I get the error that there is no matching function
> > for contentsToViewport(QPoint &) unless I explicitly use
> > QScrollView::contentsToViewport(...) which then compiles and works as
> > intended.
> >
> > I thought that it was possible to have different functions with the
> > same name as long as the parameters where different.
> >
> > Anyone have any idea why this doesn't work?
> Yes, a method in a derived class hides any method with the same name in the
> base class. You have two possibilities here:
> 
> class Base
> {
> public:
>         void doStuff( const QPoint& );
> };
> 
> // Either:
> class Derived : public Base
> {
> public:
>         void doStuff( const QPoint& p ) { Base::doStuff( p ); }
>         void doStuff( const QRect& );
> };
> 
> // Or, but doesn't work with older compilers:
> class Derived : public Base
> {
> public:
>         using Base::doStuff;
>         void doStuff( const QRect& );
> };
> 
I would expect this if the functions had identical signatures, but
where the functions are uniquely defined, I would not have thought it
a problem for the compiler to use the base class function.

Thanks for the info,  I'll use the work around for it.

Steve
 
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