Does this suit COM? - COM Discussion Boards

Re: How to pass Date/Time values in COM

11-Jun-02 9:20

If you want your COM Object to be accessible form Visual Basic use DATE data type (which is typedefed to double). Use CComDate available at http://www.sellsbrothers.com.

Mazdak11-Jun-02 9:19

Mazdak

11-Jun-02 9:19

Non-MFC Date Routines in ATL

Mazy

"The more I search, the more my need
For you,
The more I bless, the more I bleed
For you."The Outlaw Torn-Metallica

Networking question

rsasalm_10-Jun-02 20:46

rsasalm_

10-Jun-02 20:46

Hi all,

At home I want to connect atleast two to three PC's to test DCOM objects.
Right now I have a PC with winXP and other win95.
The computer with winXP is connected with 100Mbits internet connection.
Now my question is what hardware and software do I need so that I can build my own LAN.
Further I have network cards on both computers.
I would appreciate if someone can help me in this regards.

thanks in advance
regards
/rsasalm

Re: Networking question

MikeC#11-Jun-02 2:32

MikeC#

11-Jun-02 2:32

Hey there!
On the hardware side you need:
1 switch or router (preferrably with 4-8 ports or so) probably a router to get the best performance.
1 network card for each computer, see that you get enough performance here so that you can take advantage of your internet connection (100Mbps)
Off course you need to have som network cable to connect the computers to the router.

Then you just connect your internet connection to one port on the router and use one port for each pc. If you don't connect to the internet through the router then you probably can't use all your pcs on the internet

Mike

Re: Networking question

11-Jun-02 2:51

Hi Mike,

Thanks for reply.
I have one more question.
I am getting confused with the terms router, switch and hub.
Can someone explain the difference and which one is better and why, particularly in my case?

thanks
regards
/rsasalm

Forcing a COm control to exit a loop

John Oliver10-Jun-02 5:34

John Oliver

10-Jun-02 5:34

I have a MFC ActiveX component which processes a large inputfile. The component is contained in a VB form. I want to have a Cancel button on the VB form to tell the component to exit the loop.

Inside the component's main loop I'm calling PeekMessage then TranslateMessage and DispatchMessage to allow the user to interact with the VB form (otherwise it would just freeze up while the Component executes).

I imagine something like this would be the way to go:

bool CFileControl::Process()
{
while (!file.eof)
{
while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if (msg.message == WM_QUIT)//maybe used a userdefined message instead
return TRUE;

TranslateMessage(&msg);
DispatchMessage(&msg);
}
//read next line of large file and process data

}

return...

}

Is it straightforward to pass a userdefined message from VB or does this break some COM rules. Otherwise has anybody any ideas? If I maybe set a flag which the loop condition could test, must I use a separate thread in order to set this flag.
Thanks for reading this far,
John

Re: Forcing a COm control to exit a loop

Ernest Laurentin10-Jun-02 6:17

Ernest Laurentin

10-Jun-02 6:17

I think having a flag to exit the loop is better than having to send a message.
Yes, in that case you may need to have a separate thread to do (since you have a
large file...). If your control display a UI and has a button to stop the process,
you may still want to use a technic similar to the one with PeekMessage but this is
just a matter a choice. The best method in my opinion is to have a flag and use
a second thread but you will have to work a bit harder to make sure that your control
is thread safe.
Good luck!

One good thing about getting older, you don't lose the ages you've been!

Does this suit COM?

StuartHall9-Jun-02 20:59

StuartHall

9-Jun-02 20:59

Hi,

I'm an extreme newby to COM. What I want to do is be able to create a system where there are different components that manipulate an array of data. For example one might do a moving average, one might do a standard deviation etc. However I want other people to be able to develop components as well.

Could I develop a base interface and then VC++ and VB programmers could develop their components based on this interface and register somehow with my program. Then I could just have a Calculate( .. ) function and a GetDescription( .. ) function to create menus from.

Would I be better off just using dlls and using GetProcAddress?

Thanks

Re: Does this suit COM?

Rama Krishna Vavilala10-Jun-02 1:55

10-Jun-02 1:55

Since there are many functions in picture I think you should go for COM. Using COM will turn out to be simpler. Smile | :)

Casting

Justin Turney9-Jun-02 10:12

Justin Turney

9-Jun-02 10:12

I have an out-proc server i'm currently writing. In this server I have a number of interfaces. I was wondering if I could do the following. All the interfaces and implementations of the interfaces are in the same project.

interface IUser {....}; // IUser definition
interface IUsers {....}; // IUsers definitions

class CUser : public IUser {....}; // The implementation of IUser
class CUsers : public IUsers {...}; // The implementation of IUsers

HRESULT CUsers::SomeFunc() {
CComPtr<IUser> pUser;
pUser.CreateInstance(__uuidof(IUser));
((CUser*)(pUser.p))->m_SomeData; // Can I do this cast from IUser to CUser?
...
}

That was my question, is the cast possible?

Justin Turney

Paul M Watt9-Jun-02 10:23

9-Jun-02 10:23

Yes, but it is not safe.

Since you are in your CUser class when you create the new object, it would be safer to call new, then cast the object to the interface if the interface needed to be exported from the function.

HRESULT CUsers::SomeFunc()
{
    CUser pUser = new CUser;
    pUser->m_SomeData;
...
    CComPtr piUser
    piUser = static_cast<IUser*>(pUser);
...
}

Good Luck

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

Rama Krishna Vavilala9-Jun-02 10:25

9-Jun-02 10:25

Justin Turney wrote:
That was my question, is the cast possible?

Why do you want to do that?

You should never do anything like that. If a proxy or stub gets involved in between then the code will not be safe.

mhamsa10-Jun-02 2:47

mhamsa

10-Jun-02 2:47

Can't you implement a propget on IUser that returns the contents of m_SomeData?

CreateInstance does not work in MFC DLL

Vi211-Jun-02 5:17

Vi2

11-Jun-02 5:17

pUser.CreateInstance(__uuidof(IUser));

__uuidof(IUser) is the UUID of IUser interface, not the his coclass CLSID. So this call will be unsuccessful.

You can use the local creation of COM object:

CComObject < CUser >* pUser;
HRESULT hr = pUser->CreateInstance( & pUser );
if( SUCCEEDED(hr) )
{
	pUser->m_SomeData;
...
	delete pUser;
}

With best wishes,
Vita

Plugins

8-Jun-02 22:16

I get the impression that most plugins are implemented using COM, hence the posting here. Can anyone give me any headstart on implementing plugins in my application. OpenSource examples would be particularly useful.

Any tips or hints?

I Cargill CEng BENg MBCS

7-Jun-02 5:53

I have trouble creating instance of an shellwindows object in MFC dll
CreateInstance does not work in MFC DLL, but CreateInstance work well in EXE MFC

It hangs on the CreateInstance row

What could this be happening ?

/// My code //
// I Created a Dialog class in MFC DLL
BOOL CWalletDlg::ShellWindowAdvise()
{
EnableAutomation();
m_pIE5Events = new CIE5Events(this);
HRESULT hr = 0;
CoInitialize(NULL);
if (m_spSHWinds == 0) {
hr = m_spSHWinds.CreateInstance(__uuidof(SHDocVw::ShellWindows));
AfxConnectionAdvise( m_spSHWinds,
__uuidof(SHDocVw:ShellWindowsEvents),
this->GetInterface( &IID_IUnknown ),
TRUE, &m_dwCookie );
return TRUE;
}
}

Re: CreateInstance does not work in MFC DLL

Rama Krishna Vavilala7-Jun-02 6:12

Re: CreateInstance does not work in MFC DLL

7-Jun-02 6:12

Is the exe calling CoInitialize?

Paul M Watt8-Jun-02 9:07

COM+ Session With C# (NOT in ASP.Net)

8-Jun-02 9:07

More importantly, is the EXE calling CoInitialize on the thread that the DLL is loaded.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

MikeC#6-Jun-02 4:22

MikeC#

6-Jun-02 4:22

I have a little problem. The background is:
I'm working on a server/client application in C# and I want to setup up a session, but when you use COM+ you can't use a session. The client is not run in a browser.
I also have to "create" the session on the server and pass it on to the client. Anyone have a suggestion on how to implement this (NOT in ASP)?
I've been trying to com up with some constructive solution for a while now, but i hit the wall before i get any results! Mad | :mad:

MikeC#

Passing ordinary functions to COM object

Hans Ruck4-Jun-02 0:58

Hans Ruck

4-Jun-02 0:58

Is that a way to pass simple functions to COM objects like this:

ob->Method(pFunc);

where pFunc is a function like "void pFunc(void)"?
I want pFunc to be called from inside the COM object.

rechi

Rama Krishna Vavilala4-Jun-02 1:25

4-Jun-02 1:25

It is not considered a good practice to pass pointers in COM methods. Instead wrap the function as an interface

interface IMyFunc
{
HRESULT Func();
}

Just to give you an idea.
You can have

class A : IMyFunc
{
public:
void Func()
{

}
}

The method would look like

HRESULT Method(IMyFunc* pFunc);

A* pA;
.
.
.

ob->Method(pA);

Hans Ruck4-Jun-02 1:40

Hans Ruck

4-Jun-02 1:40

It's what i was the most afraid of: interfaces wrapping functions. Unfortunately this solution consumes a large amount of time.

Thanx!

rechi

Paul M Watt8-Jun-02 9:08

8-Jun-02 9:08

Bogdan Rechi wrote:
Unfortunately this solution consumes a large amount of time.

That is the price that we all have to pay for Binary Comaptible code.

Build a man a fire, and he will be warm for a day
Light a man on fire, and he will be warm for the rest of his life!

Paul M Watt8-Jun-02 9:11