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Error: "cannot instantiate abstract class"


I have the following problem:

I have a class deriving from ICustomTypeDesc riptor:

public __gc class TPropertyBag : public ICustomTypeDesc riptor

private: ...

virtual String* GetClassName(){ return
TypeDescriptor: :GetClassName(t his,true);} //[LINE 27]


When I try to instantiate it, I get the following compiler errors:

------ Build started: Project: QiCadApp, Configuration: Debug Win32


TCadInspector.c pp

d:\apps\TProper tyBag.h(27) : error C2039: 'GetClassNameA' : is not a
member of 'System::Compon entModel::TypeD escriptor'
TCadInspector.c pp(0) : see declaration of
'System::Compon entModel::TypeD escriptor'

d:\apps\TProper tyBag.h(27) : error C2660:
'TPropertyBag:: GetClassNameA' : function does not take 2 arguments

TCadInspector.c pp(11) : error C2259: 'TPropertyBag' : cannot
instantiate abstract class
due to following members:
'System::String __gc *TPropertyBag:: GetClassName(vo id)' : pure
virtual function was not defined
TCadInspector.c pp(0) : see declaration of
'TPropertyBag:: GetClassName'

Build log was saved at "file://d:\apps\Debug\B uildLog.htm"
QiCadApp - 3 error(s), 0 warning(s)


I don´t understand anything what the compiler tells me, because:

1. I have the Symbol "GetClassNa meA" anywhere in my project
2. As you can see, I overrided the virtual function "virtual String*
GetClassName()" correctly

I can remove the error 2039 and 2660 when I change the line

virtual String* GetClassName(){ return
TypeDescriptor: :GetClassName(t his,true);}
virtual String* GetClassName(){ return NULL;}

The interesting thing is, that in another project it works without any
problems. I included the unit with this code to this new project and
got these errors. Maybe there is something wrong with the project
settings of this new project but I don`t know where to search.

I hope that anyone can help me,


Nov 17 '05 #1
1 2825
Andreas Poller wrote:

I have the following problem:

You've #included <windows.h> which defines a macro GetClassName.

A simple

#undef GetClassName after the #include should do the trick.


Nov 17 '05 #2

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