🚀 go-pugleaf

<Roger Warren> wrote in message news:4154a05c$1@newsgroups.borland.com...
> Hello,
>
> I have the following class defined in TestDLLClass.h:
>
> class TestDLLClass
> {
>   public:
>     TestDLLClass();
>     virtual ~TestDLLClass();
>     virtual void TestMethod(AnsiString &s);
>
> };

To make a class exportable from a DLL, add a line like the following just
*before* the above class declaration:

class PACKAGE TestDLLClass;
class TestDLLClass
{
...
};


> The host executable uses the following to try and use the instance of
> TestDLLClass created with the dll's CreateInstanceOfTestDLLClass
> function:
>
> void __fastcall TfrmMain::Button1Click(TObject *Sender)
> {
>   HANDLE h = LoadLibrary("../DLL/somedll.dll");
>   TESTDLLCLASS CreateInstanceOfTestDLLClass =
> (TESTDLLCLASS)GetProcAddress(h, "_CreateInstanceOfTestDLLClass");
>   TestDLLClass *ptrDLLClass = CreateInstanceOfTestDLLClass();
>   ptrDLLClass->TestMethod("Hello");
>   delete ptrDLLClass;        <== *** DON'T DO THIS ***!!!
>   FreeLibrary(h);
> }

Just as you export a function to create an instance of the class, so must
you also export a function to destroy an instance of the class.  The DLL
must be responsible for allocating AND deleting the class instances.

- Dennis