ATL / WTL / STL

Re: a question about STL sort

17-Nov-02 23:51

Add a suitable comparison operator to A:

struct A
{
...
  bool operator<(const A& r) const
  {
    return nNum<r.nNum;
  }
}

and then just use std::list::sort.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Christian Graus18-Nov-02 0:56

Christian Graus

18-Nov-02 0:56

I cover this at length in my article on functors.

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

Hey, at least Logo had, at it's inception, a mechanical turtle. VB has always lacked even that... - Shog9 04-09-2002

Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002

Explicit specialization of class templates

Dudi Avramov17-Nov-02 20:33

17-Nov-02 20:33

Hi fellows,
I would like to have explicit specialization of class template CComObject
in ATL.
The reason for this is that i would like to have COM object pooling.
Therefore, if i could overwrite the CComobject::Release method then i have what i need.
However, i get compilation error when i do the following:

template<>
class CComObject<CMyCOM> : public CMyCOM
{
...
}

error C2934: 'CComObject<class cwasterecord="">' : template-class-id redefined as a nested 'class' of '<unknown>.

How can i have my CComObject specialization?

Thanks,
Dudi

Joaquín M López Muñoz17-Nov-02 21:12

17-Nov-02 21:12

Can't you do this instead?

class CMyCom:public CComObject<CMyCom>
{
  ...
  // override Release
  ...
};

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dudi Avramov17-Nov-02 22:12

17-Nov-02 22:12

No i can't, since CComObject derives from any COM object and it is the last derived class that implemenets the IUnknown methods (AddRef, Release and QueryInterface).
I thought that if i write explicit specialization for CComObject then i can get what i want.

Joaquín M López Muñoz17-Nov-02 22:53

17-Nov-02 22:53

But, if I'm not wrong, IUnknown methods are virtual, you can safely override them.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dudi Avramov18-Nov-02 1:05

18-Nov-02 1:05

Yes i know, but i am afraid that somewhere else in ATL code there is
a pointer to CComObject (the most derived class) so i want to be sure that
every call to Release will be to overwritten one.

Joaquín M López Muñoz18-Nov-02 2:25

18-Nov-02 2:25

Ok, now I think I know what you're after. You can arrange things by laying down the following hierarchy:

template <class ThreadModel> class CMyComRoot: public CComObjectRootEx<ThreadModel>
{
  // override InternalRelease
};
 
class CMyCom: public CMyComRoot<ThreadModel>, public CComObject<CMyCom>
{
  // rest of implementation
};

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dudi Avramov18-Nov-02 2:52

18-Nov-02 2:52

My COM object can overwrite InternalRelease. However, CMyCOM can't inherit from CComObject. On the contrary, CComobject inherits from CMyCOM.
If you look in <atlcom.h> you can see that CComObject derives from a COM object. It is the most derived class.
ATL sometimes works with the pointer to CComObject<> .
Therefore, i have to define explicit specialization to that template.
What is the meaning to:

error C2934: 'CComObject<class cmycom="">' : template-class-id redefined as a nested 'class' of '<unknown>'?

Joaquín M López Muñoz18-Nov-02 2:59

18-Nov-02 2:59

From the end of your post to the beginning

error C2934: 'CComObject' : template-class-id redefined as a nested 'class' of ''?

Basically, it means that you cannot specialize this, I guess because full specialization implies instantiation, and this can't be done (the same way as CComObject<CComObjectRoot> cannot be instantiated directly).

My COM object can overwrite InternalRelease. However, CMyCOM can't inherit from CComObject. On the contrary, CComobject inherits from CMyCOM.

So, if I' understanding now your intention, CMyCom is meant as a replacement for CComObjectRoot and family, right? Then, cannot you just provide a suitable InternalRelease implementation and forget about specializing?

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dudi Avramov18-Nov-02 3:19

18-Nov-02 3:19

CMyCOM is derived from CComObjectRoot family.
i can overwrite InternalRelease but it cann't help.
Here is the code of CComObject::Release:
STDMETHOD_(ULONG, Release)()
{
ULONG l = InternalRelease();
if (l == 0)
delete this;
return l;
}
CComObject::Release method decides whether to delete the object or not.
Therefore, overwriting InternalRelease can't help.

So what else can i do?

Joaquín M López Muñoz18-Nov-02 7:00

18-Nov-02 7:00

Maybe you can return a non-zero value from InternalRelease, as the life-tracking of your objects is handled internally.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Dudi Avramov18-Nov-02 20:47

Is this a bug in ATL CAxDialogImpl?

18-Nov-02 20:47

I thought about that, but the CComObject::Release should return the object to the pool instead of deleting it.
CComObject::Release should check if the reference counter is 1 then the object should be returned to the pool. (Intead of deleting it when the counter is 0).
Therefore, i must change CComObject::Release implementation.

Member 9616-Nov-02 7:33

Member 96

16-Nov-02 7:33

I have a simple dialog and a problem with ShowWindow where EnableWindow seems to work perfectly.

Specifically, the following code works perfectly:

if(strHelpID.IsEmpty())<br />
  GetDlgItem(IDC_BTN_MORE).EnableWindow(FALSE);<br />
else<br />
  GetDlgItem(IDC_BTN_MORE).EnableWindow(TRUE);

However the following code:

if(strHelpID.IsEmpty())<br />
  GetDlgItem(IDC_BTN_MORE).ShowWindow(SW_HIDE);<br />
else<br />
  GetDlgItem(IDC_BTN_MORE).ShowWindow(SW_SHOW);

causes the dialog display to go "snaky" and areas of the dialog become blank, all buttons disappear, static text boxes go blank, the background paints over everything (intermittently), in other words controls on the dialog not related to the code above for a single button are affected in how they draw.

The code above is called by the user clicking on a button which shows a tip of the day so it's not tied to an event or windows message of any kind (other than the user clicking on a button).

(This is ATL 7.0)

Need help in accessing ATL COM property of type coclass.

bahruddina15-Nov-02 5:21

bahruddina

15-Nov-02 5:21

hi,

I need a help !! Please someone help me !

I am developing ATL COM which contains property of type COM object (ATL coclass): CComObject<dombookingareaholder> *m_AreaHolder.
Just for info: domBookingAreaHolder is a ATL co class.
I want to allow all clients (C++, VB, VBSCript) to be able to get and put the property.
Below is the code for ATL COM:

1) domBooking.CPP

<br />
<br />
// domBooking<br />
class ATL_NO_VTABLE domBooking : <br />
	public CComObjectRootEx<CComSingleThreadModel>,<br />
	public CComCoClass<domBooking, &CLSID_domBooking>,<br />
	public ISupportErrorInfo,<br />
	public IDispatchImpl<IdomBooking, &IID_IdomBooking, &LIBID_DOMIBMSLib><br />
{<br />
public:<br />
	domBooking()<br />
	{<br />
	}<br />
	<br />
	HRESULT FinalConstruct()<br />
	{<br />
		CComObject<domBookingAreaHolder>::CreateInstance(&m_AreaHolder);<br />
		return S_OK;<br />
	}<br />
<br />
	void FinalRelease()<br />
	{	<br />
		m_AreaHolder = NULL;<br />
	}<br />
<br />
DECLARE_REGISTRY_RESOURCEID(IDR_DOMBOOKING)<br />
<br />
DECLARE_PROTECT_FINAL_CONSTRUCT()<br />
<br />
BEGIN_COM_MAP(domBooking)<br />
	COM_INTERFACE_ENTRY(IdomBooking)<br />
	COM_INTERFACE_ENTRY(IDispatch)	<br />
END_COM_MAP()<br />
<br />
// IdomBooking<br />
public:<br />
	<br />
	STDMETHOD(get_AreaHolder)(IDispatch*** pVal);<br />
	STDMETHOD(put_AreaHolder)(IDispatch** newVal);<br />
		<br />
	<big>CComObject<domBookingAreaHolder> *m_AreaHolder;</big><br />
<br />
};<br />
<br />

1) How I can accomplish this ?
2) how the propety for get and set being implemeted ?
3) and lastly how client can call to object property using set and put in VC++ ?

Thank u very very much in advance . Any advice and suggestions strongly aprreciated.

Regards,
Newbie

Re: Need help in accessing ATL COM property of type coclass.

Rene De La Garza15-Nov-02 10:25

Rene De La Garza

15-Nov-02 10:25

maybe read this would help: http://www.codeproject.com/atl/com_atl.asp[^]

"Now I guess I'll sit back and watch people misinterpret what I just said......"
Christian Graus At The Soapbox
[^]

Re: Need help in accessing ATL COM property of type coclass.

Dudi Avramov18-Nov-02 1:43