error C2259: cannot instantiate abstract class

Question

0.00/5 (No votes)

See more:

VS2010

I create a ATL project with Visual Studio 2010, and add a ATL simple object class in this project. There is no any error during the building process. But when I declare a class object, such as CCartoPoint pt, I get the error message "error C2259: 'CCartoPoint' : cannot instantiate abstract class"

In the following codes, the error message is from the method 'STDMETHODIMP CCartoPoint::get_Centroid( ICartoPoint** pCentroidVal)'.

I have checked the the numbers of methods in IDL file, in .h file and the .cpp file is same.

The *.IDL file:

C++

[
	object,
	uuid(14428BC6-A897-4268-8FFD-B4947DEDDFC6),
	dual,
	nonextensible,
	pointer_default(unique)
]
interface ICartoPoint : IDispatch{
	[propget, id(2)] HRESULT X([out, retval] DOUBLE* pVal);
	[propput, id(2)] HRESULT X([in] DOUBLE newVal);
	[propget, id(3)] HRESULT Y([out, retval] DOUBLE* pVal);
	[propput, id(3)] HRESULT Y([in] DOUBLE newVal);
};
[
	object,
	uuid(238155D0-220A-4BFA-90D2-46E27461E314),
	dual,
	nonextensible,
	pointer_default(unique)
]
interface ICartoGeometry : IDispatch{
	[propget, id(1)] HRESULT Area([out, retval] DOUBLE* pAreaVal);
	[propget, id(2)] HRESULT Centroid([out, retval] ICartoPoint** pCentroidVal);
	[propget, id(3)] HRESULT GeometryType([out, retval] cartoGeometryType* pTypeVal);
	//[propget, id(4)] HRESULT Coordinates([out, retval] ICartoCoordinate** pCdsVal,[out] DOUBLE* pCountVal);
	[propget, id(5)] HRESULT NumGeometries([out, retval] LONG* pNumberVal);
	[propget, id(6)] HRESULT NumPoints([out, retval] LONG* pNumberVal);
	[propget, id(7)] HRESULT Coordinates([out, retval] ICartoCoordinate** pVal);
};

The *.h file

C++

class ATL_NO_VTABLE CCartoPoint :
	public CComObjectRootEx<CComSingleThreadModel>,
	public CComCoClass<CCartoPoint, &CLSID_CartoPoint>,
	public IDispatchImpl<ICartoPoint, &IID_ICartoPoint, &LIBID_GeometryObjectLib, /*wMajor =*/ 1, /*wMinor =*/ 0>,
    public IDispatchImpl<ICartoGeometry, &IID_ICartoGeometry, &LIBID_GeometryObjectLib, /*wMajor =*/ 1, /*wMinor =*/ 0>
{
public:
	CCartoPoint()
	{
		m_pCoordinate = new Coordinate(0,0);

		GeometryFactory factory;
		m_pPoint = factory.createPoint(*m_pCoordinate);

	}

	CCartoPoint(DOUBLE x, DOUBLE y)
	{
		m_pCoordinate = new Coordinate(x,y);

		GeometryFactory factory;
		m_pPoint = factory.createPoint(*m_pCoordinate);

	}

DECLARE_REGISTRY_RESOURCEID(IDR_CARTOPOINT)


BEGIN_COM_MAP(CCartoPoint)
	COM_INTERFACE_ENTRY(ICartoPoint)
	COM_INTERFACE_ENTRY2(IDispatch,ICartoPoint)
	COM_INTERFACE_ENTRY(ICartoGeometry)
END_COM_MAP()



	DECLARE_PROTECT_FINAL_CONSTRUCT()

	HRESULT FinalConstruct()
	{
		return S_OK;
	}

	void FinalRelease()
	{
	}

public:
	STDMETHOD(get_X)(DOUBLE* pVal);
	STDMETHOD(put_X)(DOUBLE newVal);
	STDMETHOD(get_Y)(DOUBLE* pVal);
	STDMETHOD(put_Y)(DOUBLE newVal);

public:
	STDMETHOD(get_Area)(DOUBLE* pAreaVal);
	STDMETHOD(get_Centroid)( ICartoPoint** pCentroidVal);
	STDMETHOD(get_GeometryType)( cartoGeometryType* pTypeVal);
	STDMETHOD(get_NumGeometries)(LONG* pNumberVal);
	STDMETHOD(get_NumPoints)( LONG* pNumberVal);
	STDMETHOD(get_Coordinates)(ICartoCoordinate** pVal);

private:
	Point* m_pPoint;
	Coordinate* m_pCoordinate;
};

OBJECT_ENTRY_AUTO(__uuidof(CartoPoint), CCartoPoint)

The *.cpp file

C++

STDMETHODIMP CCartoPoint::get_X(DOUBLE* pVal)
{
	return S_OK;
}


STDMETHODIMP CCartoPoint::put_X(DOUBLE newVal)
{
	return S_OK;
}


STDMETHODIMP CCartoPoint::get_Y(DOUBLE* pVal)
{
	return S_OK;
}

STDMETHODIMP CCartoPoint::put_Y(DOUBLE newVal)
{
	return S_OK;
}

STDMETHODIMP CCartoPoint::get_Area(DOUBLE* pAreaVal)
{
	return S_OK;
}

STDMETHODIMP CCartoPoint::get_Centroid( ICartoPoint** pCentroidVal)
{
	CCartoPoint pt;

	return S_OK;
}

STDMETHODIMP CCartoPoint::get_GeometryType( cartoGeometryType* pTypeVal)
{
	return S_OK;
}

STDMETHODIMP CCartoPoint::get_NumGeometries(LONG* pNumberVal)
{
	return S_OK;
}

STDMETHODIMP CCartoPoint::get_NumPoints( LONG* pNumberVal)
{
	return S_OK;
}

STDMETHODIMP CCartoPoint::get_Coordinates(ICartoCoordinate** pVal)
{
	return S_OK;
}

Posted 18-Jul-13 16:01pm

Member fish

Updated 18-Jul-13 16:04pm

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

H.Brydon · Answer 1 · 2013-07-18T17:18:00

Solution 2

I didn't check if you are missing any APIs but the ATL_NO_VTABLE spec on the class definition tells the compiler that the class will not be instantiated.

[If you fix that, there still might be one or more APIs that need to be implemented...]

Posted 18-Jul-13 17:18pm

H.Brydon

Sergey Alexandrovich Kryukov · Answer 2 · 2013-07-18T16:30:00

The idea of abstract class is to limit its instantiation. Such class is not designed for having instances of it, it is designed to be used as a base class in some derived classes, some of which also may remain abstract. And abstract class may have pure abstract functions (which have their placeholder in a virtual table, but not implementation, even though they are actually used in other functions, so using instances of such classes would be dangerous. Formally, however, it's not required; a class can be abstract by design, and some functions of it can be virtual but implemented (pseudo-abstract or non-abstract).

—SA