Building the pbadd PowerBuilder extension

To implement the pbadd extension:

1. Create the pbadd.h header file.

   The pbadd.h header file declares the pbadd class. The file includes pbext.h, which must be included in all PowerBuilder extensions because it declares the ancestor classes for native classes and the standard functions that the extension must expose. Here is the code for pbadd.h:

   #include "pbext.h"
   class pbadd: public IPBX_NonVisualObject
   {
   public:
      pbadd();
      virtual ~pbadd();
      PBXRESULT Invoke(
         IPB_Session   *session,
         pbobject      obj,
         pbmethodID    mid,
         PBCallInfo    *ci);
    
      int f_add(IPB_Session*, pbint, pbint);

   
   // Enum used to provide entry points for each
   // method in the class - the only one in this case
   // is mAdd
      enum MethodIDs
      {
         mAdd = 0 
      };
    
   private:
      virtual void Destroy();
   };

2. Create the main.cpp file, which includes pbadd.h and implements the standard functions, PBX_GetDescription and PBX_CreateNonvisualObject:.

   • PBX_GetDescription is used to pass the descriptions of classes in the extension to PowerBuilder.

   • The PBX_CreateNonVisualObject method creates the object instance. The PowerScript CREATE statement maps to this PBNI method.

   The following is the code for main.cpp:

   #include "pbadd.h"
   // initialize the PBX
   BOOL APIENTRY DllMain(HANDLE hModule,
                   DWORD ul_reason_for_all,
                    LPVOID lpReserved
                 )
   {
      switch(ul_reason_for_all)
      {
         case DLL_PROCESS_ATTACH:
         case DLL_THREAD_ATTACH:
         case DLL_THREAD_DETACH:
         case DLL_PROCESS_DETACH:
            break;
      }
      return TRUE;
   }
    
   

   // describe the pbadd class
   PBXEXPORT LPCTSTR PBXCALL PBX_GetDescription()
   {
      static const TCHAR desc[]={
         "class pbadd from nonvisualobject \n" \
         "function int f_add(int a,int b)\n" \
         "end class \n"
      };
   return desc;
   }
    
   

   // export the required PBX_CreateNonVisualObject
   // function so that the PBVM can
   // create an instance of the class
   PBXEXPORT PBXRESULT PBXCALL PBX_CreateNonVisualObject
   (
      IPB_Session*    pbSession,
      pbobject        pbobj,
      LPCSTR          xtraName,
      IPBX_NonVisualObject   **obj
   )
   {
      // if the calling function requests the pbadd
      // class, create an instance
      if (strcmp(xtraName,"pbadd")==0)
         {
            *obj=new pbadd;
      }
      return 0;
   };

3. Create the pbadd.cpp file, which includes pbadd.h and contains the implementation of the pbadd class and its single method, f_add.

   #include "pbadd.h"
    
   // Implement the required Invoke method
   PBXRESULT pbadd:: Invoke(IPB_Session *Session,
      pbobject obj, pbmethodID mid, PBCallInfo *ci)
   {
      // if the method to call is f_add
      if (mid == mAdd)

      {
         int sum = f_add(Session, ci->pArgs->GetAt(0)->
            GetInt(), ci->pArgs->GetAt(1)->GetInt());
         ci->returnValue->SetInt(sum);
      }
      return PBX_OK;
   }
    
   // constructor and destructor
   pbadd:: pbadd()
   {
   }
   pbadd:: ~pbadd()
   {
   }
    
   // implement the class's f_add method
   int pbadd:: f_add(IPB_Session* session, pbint arg1,
      pbint arg2)
   {
      return arg1+arg2;
   }
    
   // Implement the required Destroy method
   void pbadd::Destroy()
   {
      delete this;
   }

To compile and link the PBX:

1. In your C++ development tool or on the command line, compile and link the PBX.

   Make sure the include directory in PowerBuilder 12.5\SDK\PBNI is in your include path. For this example, the generated DLL is called pbadd.pbx.