Managed C++/CLI

Re: assignment vs default ctor

11-Aug-07 5:19

When does the assignment operator get called as opposed to the default ctor? For example, the first line calls the default ctor while the second calls the assignment.

<br />
MyClass theObj = 5;<br />
theObj = theObj;<br />

TIA

I am a SysAdmin, I battle my own daemons.

Mark Salsbery11-Aug-07 6:55

Mark Salsbery

11-Aug-07 6:55

Like the name implies, a constructor constructs an object.

You're constructing an object on the first line.
The second line is an assignment (explicitly using the assignment operator).

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

operator++(int)

swjam11-Aug-07 4:58

11-Aug-07 4:58

why does the returned object have to be const?

<br />
const Counter Counter::operator++(int)<br />
{<br />
  Counter temp(*this);<br />
  ++itsVal;<br />
  return temp;<br />
}<br />

TIA

I am a SysAdmin, I battle my own daemons.

Re: operator++(int)

Mark Salsbery11-Aug-07 6:58

Mark Salsbery

11-Aug-07 6:58

I don't think it should be const. Where did you see that form?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: operator++(int)

BadKarma11-Aug-07 23:48

BadKarma

11-Aug-07 23:48

hi,

I think it is to prevent the following ambigius code snippit

<code>Counter count;
Counter foo = count++;  
// this is allowed 
count++++;              
// ambigious: what is incremented the second time the original counter 
//            or the return temporary Counter object</code>

codito ergo sum

RTTI dynamic_cast

swjam11-Aug-07 0:45

Re: RTTI dynamic_cast [modified]

11-Aug-07 0:45

Hi,

I have the following code that won't compile with the error:
e:\PROGRAMMING\SANDBOX\RTTI\dynamic_cast1.cpp(31): error C2683: dynamic_cast : 'A' is not a polymorphic type

<br />
#include "stdafx.h"<br />
<br />
using namespace std;<br />
<br />
//VOID<br />
class A {  };<br />
<br />
class B {  };<br />
<br />
void f()<br />
{<br />
   A* pa = new A;<br />
   B* pb = new B;<br />
   void* pv = dynamic_cast<void*>(pa);<br />
   // pv now points to an object of type A<br />
   pv = dynamic_cast<void*>(pb);<br />
   // pv now points to an object of type B<br />
}<br />
//END OF VOID<br />
<br />
int main()<br />
{<br />
  return 0;<br />
}

It's an example in VStudio and is expected to work. Can anyone help me make sense of the error message? TIA!

I am a SysAdmin, I battle my own daemons.

swjam11-Aug-07 0:51

In C++/CLI, What has replaced LOGFONT and TEXTMETRIC?

11-Aug-07 0:51

sorry I just found out the solution, to use dynamic_cast on an expression the underlying object must have at least 1 virtual function.
D'Oh! | :doh:

-- modified at 7:49 Saturday 11th August, 2007

however the following is supposed to cause a runtime exception but doesn't:

<br />
class E<br />
{<br />
public:<br />
  void func()<br />
  {<br />
    cout << "func from E" << endl;<br />
  }<br />
};<br />
<br />
class F<br />
{<br />
public:<br />
  void func()<br />
  {<br />
    cout << "func from F" << endl;<br />
  }<br />
};<br />
<br />
<br />
void f()<br />
{<br />
   E* pe = new E;<br />
   F* pf = dynamic_cast<F*>(pe);      // fails, not safe; <br />
                                      // B not derived from A<br />
}

as well as the following (works but shouldn't because pB is just an instance of B)

<br />
#include "stdafx.h"<br />
<br />
using namespace std;<br />
<br />
<br />
class B <br />
{<br />
public:<br />
  int BMem;<br />
  void funcB()<br />
  {<br />
    BMem = 2;<br />
    cout << "funcB: " << BMem << endl;<br />
  }<br />
};<br />
<br />
class D : public B <br />
{ <br />
public:<br />
  int DMem;<br />
  void funcD()<br />
  {<br />
    DMem = 4;<br />
    cout << "funcD: " << DMem << endl;<br />
  }<br />
<br />
};<br />
<br />
void f(B* pb, D* pd)<br />
{<br />
    D* pd2 = static_cast<D*>(pb);        // not safe, pb may<br />
                                         // point to just B<br />
    pd2->funcD();<br />
<br />
    B* pb2 = static_cast<B*>(pd);        // safe conversion<br />
    pb2->funcB();<br />
}<br />
<br />
int main()<br />
{<br />
  cout << "Main - Start" << endl;<br />
<br />
  B* pB = new B;<br />
  D* pD = new D;<br />
<br />
  f(pB, pD);<br />
<br />
  cout << "Main - End" << endl;<br />
}<br />

its output is:

<br />
Main - Start<br />
funcD: 4<br />
funcB: 2<br />
Main - End<br />

-- modified at 8:36 Saturday 11th August, 2007

I am a SysAdmin, I battle my own daemons.

BuckBrown10-Aug-07 12:05

How do you get screen graphics into Document?

10-Aug-07 12:05

Hi, I am using visual Studio 2005 C++/CLI. What is available to help me format my output to the printer. I keep finding read only properties. I can use PageScale() to get the display output to fit on the printed page but the printed output is "scrunched up". I have tried playing with PrinterSettings::CreateMeasurmentGraphics() with no success. Is using this function the right approach?

Thanks,

Buck

Buck

BuckBrown9-Aug-07 9:54

9-Aug-07 9:54

Hi, I'm using visual Studio C++/CLI. I found an example in Visual Basic and followed these steps. Using the Toolbox in the form designer I added printDialog1 and printDocument1 to my Form1. Then I modified printDialog1 and set the AllowSelection and AllowSomePages properties to true and the Document property to printDocument1. This association would seem to imply that printDocument1 would contain the contents of Form1 but evidently it doesn't. I set up the fileToolStripMenuItem to have a printToolStripMenuItem and then double clicked on it to get the function header and modified it as follows...

private: System::Void printToolStripMenuItem_Click(System::Object^ sender, System::EventArgs^ e)
{
if(printDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK)
printDocument1->Print();
}

This prints a blank page. How do I associate the graphics on my screen with printDocument1 so it will actually come out of the printer? I know this is probably incredibly trivial but most people don't document the trivial. For example, in order to be able to paint I needed to know the screen size. After googling "C++ .NET display size" I got no help. Then I tried "C++ .NET screen size" and still didn't find anything. After an hour or so I stumbled onto Screen::Bounds. I didn't even know the Screen class existed! I have five texts on C++ 2005 and none of them list the Screen class in the index (or a lot of other classes that I have found by accident that seem to be important or useful). So I would not be surprised if there is a command that takes the information from the screen and copies it to printDocument1, but is so basic that everyone knows how to do it already, everyone except the people that have never done it before. What's the $64,000 answer here?

Thanks

Buck

Luc Pattyn9-Aug-07 10:40

9-Aug-07 10:40

Hi Buck,

I will find you where ever you go...

For 64K$ I would say:
it all depends on the correlation between a document on screen and a document on paper.
Some programs keep them identical (e.g. MS Word can show what it will print almost
exactly). Other apps don't care, they show one thing, and print an equivalent but
completely different thing.

I have a simple case in my Sokoban article; it displays a board game (that fits on
a screen, no scrolling involved), and can print it on one page.

The essence is you reuse the code that currently sits in your OnPaint handler (it
will require a minor reorganization, splitting the top few lines from the body).

If your wafer would fit on one page, even when it needs some scrolling on screen,
I strongly suggest you have a look at my article's code.

Greetings

Luc Pattyn [Forum Guidelines] [My Articles]

this weeks tips:
- make Visual display line numbers: Tools/Options/TextEditor/...
- show exceptions with ToString() to see all information
- before you ask a question here, search CodeProject, then Google

BuckBrown9-Aug-07 11:05

9-Aug-07 11:05

I read the article and looked at the source code. It wasn't any help. There is no handler named OnPaint. Bottom line is all I can print are blank pages.

Buck

Luc Pattyn9-Aug-07 11:18

9-Aug-07 11:18

Hi Buck,

in LP_Sokoban's file Board.cs there is a line
Paint+=new PaintEventHandler(Board_Paint);
which is an alternative way to install a paint handler; in this case it is called
Board_Paint, and it expects to get two arguments, rather than one, but apart from
that it is identical to an OnPaint() method, which is the normal way of installing
a paint handler in a derived class.

And as you can see it immediately calls another method

public void Painter(Graphics g,  int panelWidth, int panelHeight, int<br />
fillPercentage, bool printing)

passing not the eventargs thing, but the
actual values it needs.

Same Painter method also gets called by PrintableBoard_PrintPage() which is the
PrintPage handler for my public class PrintableBoard : PrintDocument;
this handler too get installed explicitly, hence its name differs from OnPrintPage.

Hope this helps.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

BuckBrown9-Aug-07 11:40

9-Aug-07 11:40

Hi Luc,

Thanks for the info. While you were responding I was digging into another article that showed an additional function that I did not have called printDocument1_PrintPage(). Seeing that this function had the same general naming convention as other Form1 design controls, I went back to the Form1 design page and double-clicked on printDocument1 and the following code was added...

private: System::Void printDocument1_PrintPage(System::Object^ sender, System::Drawing::Printing::PrintPageEventArgs^ e)
{
DisplayWaferMap(e->Graphics); // I added this line and began receiving printed output
}

Granted, the size of the printed page has to be scaled correctly but at least now I am getting printed output.

Thanks again,

Buck

Luc Pattyn9-Aug-07 11:42

9-Aug-07 11:42

Seems like your e-mail notification problem got fixed ?

Luc Pattyn [Forum Guidelines] [My Articles]

directx

saisp8-Aug-07 18:22

saisp

8-Aug-07 18:22

hi i am having a 3d mesh .x file. how to load this using directx managed code. i am new to directx please help me.

c++ projects

Reet Dhiman7-Aug-07 23:43

Reet Dhiman

7-Aug-07 23:43

need help regarding a project. me n a friend of mine r thinking to make a voice for converting voice into text as our final year project can i get help regarding it, like what all r we supposed to do. plz do help me need it quick

Never follow anyone but learn from everyone

iddqd5158-Aug-07 3:26

iddqd515

8-Aug-07 3:26

good luck with that, I'm sure you won't fail to impress

originSH8-Aug-07 6:10

originSH

8-Aug-07 6:10

I don't want to crush your creativity or anything but Voice Recognition software is very hard to make. I think if you had the knowledge and skills to pull it off you wouldn't be asking here.

Thats not ment as an insult, I cirtainly couldn't pull off making that sort of software in a short time frame and probably could never pull it off by myself, just as a reality check.

You'd be much better off picking something small and simple that you can complete and do well. A large unfinished and badly coded project will get you much worse marks.

Karismatic8-Aug-07 20:24

Karismatic

8-Aug-07 20:24

For doing speech recognition you need to use the SAPI
yoou can get its SDK from this link
http://www.microsoft.com/downloads/details.aspx?FamilyId=5E86EC97-40A7-453F-B0EE-6583171B4530&displaylang=en[^]

and you can get help how to use sapi from here
http://www.codeproject.com/audio/SAPI.asp[^]

I know this is hard to make but not impossible, but i suggest you to use .Net to make ur project as it'll be easy to develop on it not c++.

Anyways best of luck.;)
Keep progressing....

Regards,
Pankaj Sachdeva

"There is no future lies in job"
"but"
"future lies in the person who holds the job"

originSH9-Aug-07 4:28

originSH

9-Aug-07 4:28

As far as I could see they wanted to write a voice to text app rather than use a voice to text component.

cannot convert parameter 1 from 'cli::array ^' to 'cli::array ^'

Jonathan [Darka]10-Aug-07 4:48

Jonathan [Darka]

10-Aug-07 4:48

Reet Dhiman wrote:
plz do help me need it quick

When I was doing my final year project, I actually had to do it myself why not try that!

You won't learn if someone does it for you, if you just want to learn how to do this (rather than us coding it) then I suggest google as your friend.

Don't want to be mean but a final year project is a test of you skill/knowledge, if someone else does it for you then you don't deserve to pass.

regards,

Jonathan Wilkes
Darka[Xanya.net]

BuckBrown7-Aug-07 12:03

Re: cannot convert parameter 1 from 'cli::array ^' to 'cli::array ^'

7-Aug-07 12:03

Hi, I am using Visual Studio 2005 C++/CLI. I am trying to pass an array from one object to another through a function. I get the above error which I find confusing because they seem to match. Why can't it convert? Or maybe you can show me the best way to copy an array of structures from Object A to Object B (because A will go away before B).

// Defined in Wafer.h -------------------------------------

value struct Die
{
int nXcoord;
int nYcoord;
int nBin;
};
array<Die>^ Failed;

void TransferFailedArray(array<Die>^ failed_die);

// Defined in FailMap.h -------------------------------------

value struct Die
{
int nXcoord;
int nYcoord;
int nBin;
};
array<Die>^ FailedDie;

// Defined in Form1.h ---------------------------------------
// Wafer^ is instantiated in Form1 constructor.

CFailMap^ FailMap = gcnew CFailMap();
Wafer->DeviceName = FailMap->DeviceName;
Wafer->LotNumber = FailMap->LotName;
Wafer->WaferNumber = FailMap->WaferName;
Wafer->TransferFailedArray(FailMap->FailedDie); // This line gives the error

// Defined in Wafer.cpp -------------------------------------

void CWafer::TransferFailedArray(array<Die>^ failed_die)
{
failed_die->Copy(failed_die, this->Failed, failed_die->Length);
failed_die->CopyTo(Failed, 0);
}

Does anyone see a problem with the syntax in here for defining the function?

Thanks

Buck

Luc Pattyn7-Aug-07 14:22

Re: cannot convert parameter 1 from 'cli::array ^' to 'cli::array ^'

7-Aug-07 14:22

Hi Buck,

I think you are looking at the wrong line.

BTW: I suggest you make Visual display line numbers (see my sig), then look at the
details of the compiler's error messages.

failed_die->Copy is not OK, Copy is a static method in the Array class;
as opposed to CopyTo which is an instance method.

Furthermore:

do you really need to copy the array ? an array is an object, so you can store
its reference as often as you want; it will get garbage collected only after all
references to it become unreachable.

So the only way I see to copy an array would be if you need two arrays that initially
contain the same data, but then go live their separate lives, and may be modified
independently from one another.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

BuckBrown8-Aug-07 5:37