Question

I have a SDK (GigE C++), which defines a class like this:

class PV_BUFFER_API PvBuffer
 {

public: 

 PvBuffer();
 virtual ~PvBuffer();
 PvPayloadType GetPayloadType() const;
 #ifndef PV_NODEPRECATED
 PvResult Alloc( PvUInt32 aSizeX, PvUInt32 aSizeY, PvPixelType aPixelType );
};

The document of the SDK says:

 PvResult PvBuffer::Alloc  ( PvUInt32  aSizeX,  
 PvUInt32  aSizeY,  
 PvPixelType  aPixelType   
 )    

 Allocates memory for this PvBuffer. 

 Parameters:
 [in]  aSizeX  The width of the image, in pixels. See GetWidth.  
 [in]  aSizeY  The height of the image, in pixels. See GetHeight.  
 [in]  aPixelType  The GEV pixel type from which the pixel depth is extracted. For     
 supported pixel types, see PvPixelType.h. 

 Returns:
 Includes:
 PvResult::Code::OK 
 PvResult::Code::NOT_ENOUGH_MEMORY 

I want to use the function Alloc (see the last function in the class). So I am writing like this the program:

 PvBuffer *lBuffer;  //Class name is PvBuffer
 PvResult lResult= lBuffer.Alloc( 1224, 1029,  PVPIXELMONO );

But it is giving errors, one of those is:

error C2228: left of '.Alloc' must have class/struct/union   

Is syntax correct? Why it is asking for the class?What is the correct way?

Answer 1

PvBuffer *lBuffer;  //Class name is PvBuffer
PvResult lResult= lBuffer.Alloc( 1224, 1029,  PVPIXELMONO );

leaving aside that this invokes undefined behavior, as lBuffer isn’t initialized, you want:

PvResult lResult= lBuffer->Alloc( 1224, 1029,  PVPIXELMONO );

because lBuffer is a pointer.