C / C++ / MFC Discussion Boards

safee ullah23-Dec-03 0:22

23-Dec-03 0:22

hi there..

guys i wanted to know if u have a control and u place it in a container, but the control doesnt show rather just a boundary rectangle is visible..but when i execute the container with the control..the container is visible..

is it something to do with designmode or something or something else??

thanks

Re: strange problem with activex control

Monty²23-Dec-03 1:12

Monty²

23-Dec-03 1:12

In the OnPaint of ur ActiveX Control you have to draw seperatly for Design mode as well

Live as if your were to die tomorrow. Learn as if you were to live forever.
-Mahatma Gandhi

Tricky Question

SiddharthAtw22-Dec-03 23:59

SiddharthAtw

22-Dec-03 23:59

class c{
public:
a();
b();
};

main()
{
class c *pc = 0;
pc->a() //works
}

class c{
int i;
public:
c(0):i=0;
a();
b();
};

main()
{
class c *pc = 0;
pc->a(); //doesn't work fires exception
}
why? Frown | :(

Re: Tricky Question

jhwurmbach23-Dec-03 0:14

jhwurmbach

23-Dec-03 0:14

Because you are invoking a function (a()) on a pointer that was specifically made invalid (set to 0).

Who is 'General Failure'? And why is he reading my harddisk?!?

Re: Tricky Question

Ian Darling23-Dec-03 0:16

Ian Darling

23-Dec-03 0:16

What's the definition of function a()?

Contrary to popular belief, while you can call a member function through a null pointer, it only works if you don't need to access any member variables or virtual functions (essentially, you don't need to dereference this).

If a() uses the i integer in the second example, then you are trying to access a variable through a dereferenced null pointer, which obviously will fall over.

--
Ian Darling
"The moral of the story is that with a contrived example, you can prove anything." - Joel Spolsky

Re: Tricky Question

Monty²23-Dec-03 1:08

Monty²

23-Dec-03 1:08

Bravo

Live as if your were to die tomorrow. Learn as if you were to live forever.
-Mahatma Gandhi

Re: Tricky Question

SiddharthAtw23-Dec-03 1:59

SiddharthAtw

23-Dec-03 1:59

Can U clarify on the matter of this. Please, I know what U told is correct but not able to understand 'you don't need to dereference this'.

Re: Tricky Question

Ian Darling23-Dec-03 2:14

Ian Darling

23-Dec-03 2:14

SiddharthAtw wrote:
Please, I know what U told is correct but not able to understand 'you don't need to dereference this'.

When you call a member function, that function has access to an intrinsic pointer called "this", which is a pointer the object you called the method on.

So in a hypothetical example:

// we have some class called c

int main()
{
  c myObject;
  myObject.a();  // the this pointer in a() below will be &myObject
  c *myPointer = new c;
  myPointer->a(); // the this pointer in a() below will point to the same object as myPointer
  c *myNullPointer = 0;
  myNullPointer->a(); // the this pointer in a() below is null, so accessing i through it will result in an access violation.
}

void c::a()
{
  // these two lines are equivalent.  When referring to a member variable in a
  // member function, there is an implicit "this->" before it.
  this->i = 1;
  i = 1;
}

--
Ian Darling
"The moral of the story is that with a contrived example, you can prove anything." - Joel Spolsky

Re: Tricky Question

SiddharthAtw23-Dec-03 18:11

SiddharthAtw

23-Dec-03 18:11

Thanx for making it Crystal Clear.

How can u initialize member variable while declaring???

abudu23-Dec-03 1:14

abudu

23-Dec-03 1:14

Not tricky, it is just basic. Second case will not work... how can you initalize the member variable 'i' while declaring it in the class c,u have to use constructor to initialize it. There is nothing to do with null class pointer. In both cases u have to define the functions a() and b() before calling them.

when going gets tough the tough gets going

Re: How can u initialize member variable while declaring???

SiddharthAtw23-Dec-03 2:04

SiddharthAtw

23-Dec-03 2:04

I agree with U. But my intention was about null pointer thing. If U have any please tell me

first feed the pointers

abudu23-Dec-03 17:14

abudu

23-Dec-03 17:14

As far as VC++ 6.0 is concerned it is working i.e. null pointer can be used to call the member function but it is not advisable. it may work in few compilers but it is not standard, u shud always initialize the pointer to some valid memory location of this class C type that is what we call initialization of pointer. it could be any pointer for that matter u shud make it point to a valid memory location of its type. when u go for big programs, in the sense, if u use lot of pointers with huge data and dereference it, u may get into Access violation errors and some ugly errors. Please feed the pointers with valid memory location(food) and ask it to work.

when going gets tough the tough gets going...

Re: Tricky Question

nde_plume23-Dec-03 4:13

nde_plume

23-Dec-03 4:13

You are using undefined behavior, that is why it doesn't work.
Calling a member function through a null pointer is invalid,
so the fact that two different invalid behaviors are different
is a minor matter of compiler specific details.

To put it another way, both pieces of code are not valid C++,
and consequently the discussion of different behaviors is irrelevant,
Visual Studio 8.0 could give you completely different results (in
fact a good C++ lint program would detect this error and report it
to you.)

If it is your goal to call a class defined function without a
specific instance of the object you need to use a static member
function, viz:

class c { public: static void a(); };

main()
{
c::a();
}

printer problem

skpanda22-Dec-03 23:52

skpanda

22-Dec-03 23:52

hello,
here is a prob.

suppose i will print a document. the printer spoller collects all the datas & my program in WIN32 can trap all the datas in the spoller.

here i m getting total no of pages in one document for a particular print job.but i want the following...

1. suppose i will give 2 copies (more than 2 copies) in the
print dialog and put sufficient paper in tray than it is not giving the total no of pages to be printed. WHY /???

2. if any one knows how to calculate the total no of pages printed for a job (with single copy as well as multiple copies) than please help in this regards....

here i m taking ENUMPRINTERS & ENUMJOBS APIs for all the information .

i m getting all the spoller information in ENUMJOBS.except the no of pages ....i m testing in samsung ML-4600 PCL 6 printer.

is the page count is printer specific ? i dont think so ...
otherwise no apis should have a data like pagecount...or so..

if any one knows please try to solve this prob 7 quickly inform me ...

if any information is required from my side ,,,i will help...

regards
skpanda

Outlook add in - need guru's help

YaronNir22-Dec-03 23:23

YaronNir

22-Dec-03 23:23

Hi all,

i've added an item to the 'File' meun of outlook.

i can set the property 'ShortcutText' to be something like "Ctrl+Shift+M".
if i do that, i see this string near the menu item, when i open the file menu.

problem is when i press 'Ctrl+Shift+M' combination nothing happens?

what should i do?

thanks

Ask not what your application can do for you,
Ask what you can do for your application

Database file index error

Shanmuga Sundar22-Dec-03 23:19

Shanmuga Sundar

22-Dec-03 23:19

Hai guts.,

I had an problem while indexing an mdb file with dao connection

int CTruckRecord::OpenFiles()
{
try
{
//open the database
Dccdb.Open("\\ibp-naga\\naga\\dbs\\dccclient.mdb");

//open the individual table
TruckTbl.Open("TruckRecord");

//to retrive records from the database table, you should open it

CDaoRecordset::Open(&TruckTbl);

//to set current index for table type record sets,
SetCurrentIndex("TRK_NDX");
}

catch( CDaoException* e )
{
//an exception object for DAO classes which will report error occured
//and delete it afterwards immediately. These are member functions of
//the CException class, the parent class for CDaoException
e->ReportError();
e->Delete();
return FALSE;
}
return TRUE;
}

While executing the above code. The exception handling catch an error at the line

SetCurrentIndex("TRK_NDX");

Display the error as below:
"TRK_NDX@ isn't an index in this table. look in the indexes collection of the tabledef to determine the valid index names"

Any one could say wat this line mention.

Thanx in advance.

bye.,
Shanmuga Sundar.V

required info about projects in c++

ammad ami22-Dec-03 22:54

ammad ami

22-Dec-03 22:54

i am student at graduate level and i have a need of projects ideas in clips (A.I).

Re: required info about projects in c++

Brian Shifrin23-Dec-03 5:58

Brian Shifrin

23-Dec-03 5:58

A.I?

Stock trading systems,
Power switches
Router links status info
CPU branch predictions
MxN queues (M people in N lines at the register)
Traffic control sytems.

Visual C++ link with Visual basic 6?

Anonymous22-Dec-03 21:56

Anonymous

22-Dec-03 21:56

Do anyone know how to link a Visual C++ program to a interface which is created by Visual basic 6?

i use visual C++ to create a random letter, then i need it to be able to output in my visual basic 6's interface..

Re: Visual C++ link with Visual basic 6?

jhwurmbach22-Dec-03 22:43

jhwurmbach

22-Dec-03 22:43

You could always man that massive gun named COM and aim it at your problem...

Who is 'General Failure'? And why is he reading my harddisk?!?

Re: Visual C++ link with Visual basic 6?

Anthony_Yio23-Dec-03 1:09

Anthony_Yio

23-Dec-03 1:09

Write your VC app as dynamic link library (DLL)
and export the function u want.

Sonork 100.41263:Anthony_Yio

Please help on how to update my Platform SDK!

twing22-Dec-03 21:32

twing

22-Dec-03 21:32

when i compiled some program,
the output in debug show :
"You are not using the latest Platform SDK header/library "
"files. This may prevent the project from building correctly."

failed to compile it.

and the origin code is:

#ifndef WT_EXECUTEINPERSISTENTIOTHREAD
#pragma message("You are not using the latest Platform SDK header/library ")
#pragma message("files. This may prevent the project from buildingcorrectly.")
#endif

could u tell me how to solve my problem and explain what it's in?
Thank u!

Hello World!

Re: Please help on how to update my Platform SDK!

Michael P Butler23-Dec-03 1:01

Michael P Butler

23-Dec-03 1:01

http://www.microsoft.com/msdownload/platformsdk/sdkupdate/[^]

Michael

Snow is lying on the ground, and in the air the sleigh bells sound,
The frosted patterned window panes, it's British summer time again.
No, it's not, It's Christmas - Santa Claus in on the Dole (Spitting Image 1986)

Retreive the conent MFC Active Document Server

Member 52603722-Dec-03 19:33

Member 526037

22-Dec-03 19:33

How can I retrieve the content of MFC Active Document Server?

I create my own editor using rich textbox. The editor is also an Activex container.
I can insert one Active Document Server in the rtf documnet. After saving the file as rtf format. I can not retrieve the content of rtf file for conversion to other format.

Can any one help on this regard..
Thanks in advance.

Retreive the conent MFC Active Document Server

Member 52603722-Dec-03 19:09

Member 526037

22-Dec-03 19:09

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.