cpp, Transcrypt code form delphi to C++Builder

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cpp >> Transcrypt code form delphi to C++Builder

by Didier » Wed, 18 Oct 2006 15:39:52 GMT

Hello
I want to use an object (imported from an wayx.ocx component ocx) in my
C++Builder
I have used it in delphi IDE without any problem but I can't find right
syntax to use it under C++Builder
For information this object calculate distance beetween two geographic
points
Here is the code under Delphi
var
myGeoAlgo: IOleGeoAlgo;

In my procedure
myGeoAlgo:= IOleGeoAlgo(CreateOleObject('WayX.GeoAlgo'));
myGeoAlgo.Lati1=41;
myGeoAlgo.longi1=5;
myGeoAlgo.Lati2=42;
myGeo.Algo.longi2=6
myGeoAlgo.Calculer();


So I've written under c++BUilder

IOleGeoObject *myGeoAlgo;
myGeoAlgo=IOleGeoAlgo(CreateOleObject("WayX.GeoAlgo"));

if i compile this I get the next error message at the compilation
[C++ Erreur] Unit1.cpp(23): E2352 Impossible de crr une instance de la
classe abstraite 'IOleGeoAlgo'
[C++ Erreur] Unit1.cpp(23): E2353 La classe 'IOleGeoAlgo' est abstraite
parce que '__stdcall IDispatch::GetTypeInfoCount(unsigned int *) = 0'

if I try
IOleGeoObject *myGeoAlgo;
myGeoAlgo.lati1=45.2
i get an error EAccesViolation

if I try
Variant toto;
toto = CreateOleObject("WayX.GeoAlgo");
toto.OlePropertySet("Lati1",45);
i get the same Acces violation at the run time

Can anybody help me to find the right syntax


IOleGeoAlgo *myGeoAlgo ;
toto = CreateOleObject("WayX.GeoAlgo");
toto.OlePropertySet("Lati1",12);





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cpp >> Transcrypt code form delphi to C++Builder

by Duane Hebert » Wed, 18 Oct 2006 17:55:33 GMT






Don't know why it works in Delphi but...


The compiler is telling you that it's an abstract class.
At this point, let's assume that the compiler is correct.

This means that it has at least one pure virtual function.
A pure virtual function is declared as:
virtual type functionname = 0;
like:
virtual int doSomething() = 0;

The compiler is being nice and telling you that
IDispatch::GetTypeInfoCount() is pure virtual.
This implies that IOleGeoAlgo is derived from
IDispatch and that it hasn't implemented this
pure virtual function. This makes IOleGeoAlgo
abstract as well.

If IOleGeoAlgo is your class, you must implement
GetTypeInfoCount(). If it's not your class, you
need to subclass it and provide an implementation
there for this function.


Here, you're trying to use an unitialized
pointer. You need to instantiate myGeoAlgo.



Don't know what CreateOleObject() is or does.
Probably tries to create an instance of an object
and returns 0 on failure, but that's just a guess.





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cpp >> Transcrypt code form delphi to C++Builder

by Remy Lebeau (TeamB) » Thu, 19 Oct 2006 00:43:44 GMT






Try this:

_di_IOleGeoAlgo myGeoAlgo;

myGeoAlgo = CreateOleObject("WayX.GeoAlgo");
myGeoAlgo->Lati1 = 41;
myGeoAlgo->longi1 = 5;
myGeoAlgo->Lati2 = 42;
myGeoAlgo->longi2 = 6
myGeoAlgo->Calculer();


Gambit



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Transcrypt code form delphi to C++Builder

by Didier » Thu, 19 Oct 2006 14:25:45 GMT

I've tried it but the commpilation makes the next error on _di_IOle....
Symbol _di_IOle... not defined




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Transcrypt code form delphi to C++Builder

by Remy Lebeau (TeamB) » Fri, 20 Oct 2006 01:09:34 GMT






Then you need to look in the .h file for the OCX to see what the wrapper
class is actually declared as. I might be IOleGeoAlgoPtr or
TCOMIOleGeoAlgoPtr or something like that. Look for a typedef that is using
either the DelphiInterface or TComInterface class.


Gambit



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Transcrypt code form delphi to C++Builder

by Muzaffar Mahkamov » Sat, 21 Oct 2006 03:17:15 GMT





Shouldn't it be:

IOleGeoObject *myGeoAlgo;
myGeoAlgo=(IOleGeoAlgo*)CreateOleObject("WayX.GeoAlgo");

In your code you're trying to create an object of IOleGeoAlgo class
which is not possible because it's an interface, usually with pure
virtual methods.

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Transcrypt code form delphi to C++Builder

by Remy Lebeau (TeamB) » Sat, 21 Oct 2006 04:51:14 GMT






That would not work. CreateOleObject() returns a _di_IDispatch, which will
not know how to be casted to a IOleGeoAlgo* directly. You must call the
IDispatch's QueryInterface() method (either directly or indirectly) in order
to cast an interface pointer from one type to another safely.


Gambit



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