C / C++ / MFC

COleVariant Empty bstrval

13-Jan-06 5:35

I have a small problem that I cannot find concerning GetItemDataPtr/SetItemDataPtr for the ComboBox.

I do something like this to insert an item :

/// p is a struct that also contains a name
void MyCombo::InsertString( MyPointer* pMyPointer  )
{
  int iIndex = AddString( pMyPointer ->name );
  SetItemDataPtr( iIndex, pMyPointer );

// if I do a GetItemDataPtr here, to test, the pointer is valid.
}

and this to get the data.
/// p is a struct that also contains a name

MyPointer* MyCombo::InsertString( int iIndex )
{
  // index is valid.
  MyPointer* p = ( MyPointer*) GetItemDataPtr( iIndex );
}

at this point, the pointer in the combobox is invalid ( 0x00000001 ) Confused | :confused:

I'm not certain where to start looking for clue to why this happens.

Thanks for info, tips, insights.

Max.

Edit :
Ok, Found the problem, someone else is doing a SetItemData somewhere else, and overwrites the pointer !!!! D'Oh! | :doh:

Maximilien Lincourt
Your Head A Splode - Strong Bad

-- modified at 13:33 Friday 13th January, 2006

TWS_Dave13-Jan-06 5:34

TWS_Dave

13-Jan-06 5:34

I am getting data from a database via CDaoRecordset. The data is coming back in a COleVariant from which I am reading it. However some of the fields in the database are empty which means the COleVariant is also empty. When I try to read an empty COleVariant the program crashes. This occurs when I try to convert the data to a string or date etc.

CString vData;
COleVariant vVarData;

vData = V_BSTRT(&vVarData); //crashes here if the string is empty!!

This works perfectly if the database field and thus the COleVariant is not empty. Does anybody know how to detect an empty COleVariant before trying to actually read it?

Your help would be appreciated

Dave Collins

Re: COleVariant Empty bstrval

James R. Twine13-Jan-06 6:58

James R. Twine

13-Jan-06 6:58

   You should be checking the type of the underlying VARIANT object to see if its type is VT_EMPTY or not. You can use the V_VT macro for this.

   IMHO, you should be validating the type of the VARIANT before trying to obtain its value.

   Peace!

-=- James

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Re: COleVariant Empty bstrval

Stephen Hewitt14-Jan-06 2:22

Stephen Hewitt

14-Jan-06 2:22

If you're using the V_BSTRT macro to access the data you should check that the data in the variant is actually a BSTR using the V_VT macro, like this:

<code>if ( V_VT(&vVarData) == VT_BSTR )
{
    CString vData = V_BSTRT(&vVarData)
}
else
{
    // Not safe to use "V_BSTRT(&vVarData)" here - Data not a BSTR!
}

If you use it as a BSTR when it's not you're effectiely doing a cast. For example, if the variant contains data of type VT_I4 and you treat it as a BSTR something this like is happening:

<code>UINT i = 4; // Represents the data in the variant.
CString s = reinterpret_cast<BSTR>(i)

Which would be bad.

Steve

Re: COleVariant Empty bstrval

TWS_Dave14-Jan-06 4:57

TWS_Dave

14-Jan-06 4:57

Hi Guys

Thanks for the advice

I tried validating using VT_Empty but discovered that the COleVariant was coming through with the vt value set to VT_NULL. By checking for both VT_EMPTY and VT_NULL I can manage the reading fo the data in a sensible way.

Also thanks for the comment about checking that the varinat is BSTR - I have added this to my code. One day I will grow up to be a real programmer!!

Cheers Guys - Hope I can return the help one day...

Dave Collins Smile | :)

Shockwave Flash Control

zubair_ahmed13-Jan-06 3:31

zubair_ahmed

13-Jan-06 3:31

How can i detect that a flash movie has finished/completed in shockwave flash control,so that i can load a new movie?
thanx in Advance.. Smile | :)

for those who dont know that how it is related to VC,the answer is i am using shockwave object in vc,so i need to handle it in vc. Smile | :)

zubair ahmed

-- modified at 23:36 Friday 13th January, 2006

Prakash Nadar13-Jan-06 5:30

Prakash Nadar

13-Jan-06 5:30

zubair_ahmed wrote:
How can i detect that a flash movie has finished/completed in shockwave flash control,so that i can load a new movie?
thanx in Advance..

How is this related to VC++?

-Prakash

Maximilien13-Jan-06 6:36

13-Jan-06 6:36

Mr.Prakash wrote:
How is this related to VC++?

I don't know, maybe there's a callback from the activeX control that says if the movie has finished playing ?

Maximilien Lincourt
Your Head A Splode - Strong Bad

Prakash Nadar13-Jan-06 6:38

Prakash Nadar

13-Jan-06 6:38

Maximilien wrote:
I don't know

its obvious, coz he has the problem Wink | ;)

-Prakash

zubair_ahmed13-Jan-06 20:32

zubair_ahmed

13-Jan-06 20:32

Still to get an answer.

Z.A

Re: Opening an URL in MFC

Stephen Hewitt14-Jan-06 2:26

Stephen Hewitt

14-Jan-06 2:26

It's an ActiveX control so I'd use the OLE viewer that comes with visual studio to have a peek at its type library. Look for out going interfaces. Once you find the correct out going method (assuming one exists) you'll probably have to use connection points to hook up your sink (which ypu'll have to implement). How you do this will depend to what libraries you using (or not using). e.g. ATL and MFC have different ways of going about this.

Steve

Opening an URL in MFC

Aryan S13-Jan-06 3:04

Aryan S

13-Jan-06 3:04

hi,
i m facing prblm while opening an url through mfc. i wanna open one exixsting webpage (say http://www.msn.com) on one button click. i have used OpenURL method of MFC. Its returning success. But the webpage is not opening. i wanna know what exactly i should do to open the webpage also.

Maximilien13-Jan-06 3:16

Re: Opening an URL in MFC

13-Jan-06 3:16

you can use ShellExecute

something like :
::ShellExecute(AfxGetMainWnd()->GetSafeHwnd(), "open", "http://www.msn.com", NULL, NULL, SW_SHOW);

Maximilien Lincourt
Your Head A Splode - Strong Bad

ThatsAlok15-Jan-06 19:08

ThatsAlok

15-Jan-06 19:08

Aryan S wrote:
i have used OpenURL method of MFC. Its returning success.

OpenUrl method of which class CInternetSession or CHtmlEditDoc.. if you are using CInternetSession, then it will give you pointer to file of webpage..
or if you using CHtmlEditDoc one, then you need a View derived with same in your project

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VC Forum Q&A :- I/ IV

Around 500 controls in a Dialog

AnsGe13-Jan-06 3:03

AnsGe

13-Jan-06 3:03

Hi,

how can i place around 500 controls simultaneously on a single Dialog?

Any idea?

Thanks in advance.

Anish.

toxcct13-Jan-06 3:10

toxcct

13-Jan-06 3:10

you can, but you won't be able to place all of them at design, because the editor is limiting you.

add the additionnal controls it at runtime...

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VisualCalc 3.0]

Maximilien13-Jan-06 3:13

13-Jan-06 3:13

AnsGe wrote:
500 controls simultaneously on a single Dialog?

OMG, I hope that I will never use your application.

but on a more serious note, explain what you want to do, maybe there are better ways that we could suggest.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Rajesh R Subramanian13-Jan-06 18:55

Rajesh R Subramanian

13-Jan-06 18:55

Maximilien wrote:
OMG, I hope that I will never use your application.

LMAO

You have an apple and me too. We exchange those and We have an apple each.
You have an idea and me too. We exchange those and We have two ideas each.