Re: Question about auto_ptr - C / C++ / MFC Discussion Boards

Re: I am Sergeant Destructor! (best practice Q)

BlackSmith30-Jul-02 3:40

30-Jul-02 3:40

The ~() is called when:

1. Object goes out of scope.
2. <if dinamically="" alloctade="" by="" 'new'="" operator=""> Using 'delete' operator.
3. Can be called manually.

* It's a good way for deallocating the object's resources inside the ~().

Hope this helps.

--BlackSmith--

"With the help of all mighty", 2001, Me.

Re: I am Sergeant Destructor! (best practice Q)

Andrew Peace30-Jul-02 7:27

Andrew Peace

30-Jul-02 7:27

When we used to use the Win32 API and normal C++, you would clean up everything in the destructor that was allocated within the class, e.g. delete all the memory you'd used for an array or something:

class MyClass 
{
public:
   int *m_pMyArray;

   MyClass() { printf("Hello!\n"); m_pMyArray = new int[200]; }
   ~MyClass() { printf("Bye!\n"); delete[] m_pMyArray; }
};

You'd probably put error checking in there too of course. Anyway, if we used this class as follows:

int main() 
{
   MyClass mc;
   printf("In the middle of main...\n");
}

we would get this output:

Hello!
In the middle of main...
Bye!

However, and don't quote me on this, I believe that you have to use the Finalize (don't you hate those American spellings?) method instead, and treat it as if it were a destructor. This is due to the garbage collection that takes place. The difference between the destructor in C++ and the Finalize method in MC++ is that Finalize could be called at an indeterminate time after the object goes out of scope.

Phew! Nish will probably be able to give you a better summary of the managed side of things than me.

--
Andrew.

Re: I am Sergeant Destructor! (best practice Q)

Paul Watson30-Jul-02 11:35

Paul Watson

30-Jul-02 11:35

Andrew Peace wrote:
Phew! Nish will probably be able to give you a better summary of the managed side of things than me

LOL, no you did a great job Andrew, so thank you Smile | :)

Chris was telling me about that weird "when shall she blow?" behaviour fo Finalize. Seems awfully dodgy if you ask me hehe.

There is a lot of "slipping through the cracks" stuff in C++ that I have NEVER come across in other languages. VB and C# are water tight (unless you do really daft stuff) but C++ has wyrd waters flowing through it's veins.

Thanks Andrew, will give what you said a bash.

regards,
Paul Watson
Bluegrass
Cape Town, South Africa

The greatest thing you'll ever learn is just to love, and to be loved in return - Moulin Rouge

Alison Pentland wrote:
I now have an image of you in front of the mirror in the morning, wearing your knickers, socks and shoes trying to decided if they match!

CEdit style

Renjith Ramachandran29-Jul-02 23:46

Renjith Ramachandran

29-Jul-02 23:46

in my application ,all the controls are loaded by reading a file.and in that file i specify the control type,ID ,dimension and styles...In some editbox i want to restrict the user to enter only the numbers...i found many edit styles such as ES_CENTER,ES_LEFT,ES_MULTILINE etc..which one is for the the Editbox which accept only the numbers?? any idea???????

Renjith-CPian.

Re: CEdit style

PJ Arends30-Jul-02 0:28

PJ Arends

30-Jul-02 0:28

ES_NUMBER

#define ES_NUMBER 0X2000L

CPUA 0x5041

Sonork 100.11743 Chicken Little

"So it can now be written in stone as a testament to humanities achievments "PJ did Pi at CP"." Colin Davies

Within you lies the power for good - Use it!

Re: CEdit style

Renjith Ramachandran30-Jul-02 0:49

Renjith Ramachandran

30-Jul-02 0:49

Thanks Arends....

Renjith-CPian.

Question about auto_ptr

pankajdaga29-Jul-02 23:33

pankajdaga

29-Jul-02 23:33

Hello everyone,

I have a question about the STL auto_ptr class. The following code works:

auto_ptr <complex> testPass();

int main()
{
cout << "Program started. Tesing complex numbers... \n";
cout << testPass()->Im() <<"\n";
return 0;
}

auto_ptr<complex> testPass()
{
auto_ptr <complex> test1(new Complex(3.0, 4.0));
cout << test1->Im() << "\n";
return test1;
}

How is it that I can pass an auto_ptr between functions. Shouldn't the test1 object go out of scope now and hence get destroyed. If the auto_ptr does get passed between scopes, when does it get out of scope and the destructor for Complex is called??

Thanks Rose | [Rose]

,

Pankaj

Without struggle, there is no progress

Re: Question about auto_ptr

Daniel Lohmann30-Jul-02 2:25

Daniel Lohmann

30-Jul-02 2:25

pankajdaga wrote:
ow is it that I can pass an auto_ptr between functions. Shouldn't the test1 object go out of scope now and hence get destroyed. If the auto_ptr does get passed between scopes, when does it get out of scope and the destructor for Complex is called??

This is because std::auto_ptr maintains an owner flag. Always the last auto_ptr that has been used as L-value is the current owner, all other do not destroy the object.

In your TestPass you use a local variable and return it. At this moment a new instance is created via the copy-constructor and gains ownership. Afterwards the local auto_ptr is destroyed, but does not delete the object because it is not the owner any more.

--

Daniel Lohmann

http://www.losoft.de

Multi-SDI with MFC

Kirill Kovalenko29-Jul-02 22:56

Kirill Kovalenko

29-Jul-02 22:56

Is there a way to create a Multi-SDI appication with MFC? WTL is supported it. I've made a search at the www.google.com, but haven't managed to find examples or articles. Does this mean that MFC have some internal problems to apply such a technique?

Re: Multi-SDI with MFC

Alexandru Savescu29-Jul-02 23:29

Alexandru Savescu

29-Jul-02 23:29

Could you please explain what Multi-SDI means? Is that MDI?

Best regards,
Alexandru Savescu

Re: Multi-SDI with MFC

Kirill Kovalenko29-Jul-02 23:38

Kirill Kovalenko

29-Jul-02 23:38

Multi-SDI is not MDI.
It's a group of SDI applications running in the context of single process. So the can share all the internal data and structures and this way save memory and other resources. Good example of a Multi-SDI application is Internet Explorer

Re: Multi-SDI with MFC

[James Pullicino]30-Jul-02 2:43

[James Pullicino]

30-Jul-02 2:43

Create an SDI app with MFC App Wizard.
Go to you app init instance and look for this code:

pDocTemplate = new CSingleDocTemplate(<br />
    IDR_MAINFRAME,<br />
    RUNTIME_CLASS(CMSDIDoc),<br />
    RUNTIME_CLASS(CMainFrame),       // main SDI frame window<br />
    RUNTIME_CLASS(CMSDIView));<br />
AddDocTemplate(pDocTemplate);

Make a copy of that code and paste it right below it. That should be enough to get you started. Your code should now look like this:

<br />
	// Register the application's document templates.  Document templates<br />
	//  serve as the connection between documents, frame windows and views.<br />
<br />
	CSingleDocTemplate* pDocTemplate;<br />
	pDocTemplate = new CSingleDocTemplate(<br />
		IDR_MAINFRAME,<br />
		RUNTIME_CLASS(CMSDIDoc),<br />
		RUNTIME_CLASS(CMainFrame),       // main SDI frame window<br />
		RUNTIME_CLASS(CMSDIView));<br />
	AddDocTemplate(pDocTemplate);<br />
<br />
	pDocTemplate = new CSingleDocTemplate(<br />
		IDR_MAINFRAME,<br />
		RUNTIME_CLASS(CMSDIDoc),<br />
		RUNTIME_CLASS(CMainFrame),       // main SDI frame window<br />
		RUNTIME_CLASS(CMSDIView));<br />
	AddDocTemplate(pDocTemplate);<br />
<br />
<br />
	// Parse command line for standard shell commands, DDE, file open<br />
	CCommandLineInfo cmdInfo;<br />
	ParseCommandLine(cmdInfo);<br />
<br />

James

Drinking In The Sun
Forgot Password?

Re: Multi-SDI with MFC

Kirill Kovalenko30-Jul-02 3:30

Kirill Kovalenko

30-Jul-02 3:30

Thank you!
Good trick, but it's still not the stuff which I need. It uses one thread and I can open as many new windows as many times I called AddDocTemplate. And when I close first window the rest of windows close too.

Re: Multi-SDI with MFC

Giles30-Jul-02 7:47

Giles

30-Jul-02 7:47

MFC7 has this as in Office 2000 apps.

HELP!!!! ActiveX in Visual C++

mistika29-Jul-02 22:51

mistika

29-Jul-02 22:51

I've generated an ActiveX with Visual C++, it works fine on TestContainer and Visual Basic Forms, but when I put it on a SDI Visual C++ Project in a CFormView it doesn´t work fine.
The buttoms contained in the control ActiveX doesn´t work and it goes to sleep.

Please, Can anybody help me???

Thanks in advance!!!!!

Re: HELP!!!! ActiveX in Visual C++

KingsGambit30-Jul-02 6:29

KingsGambit

30-Jul-02 6:29

In the control's OnCreate function, put ModifyStyleEx(WS_EX_CONTROLPARENT);

Try it. It may work.

Best of luck,

Rejeesh.T.S

How to change value of member within object within CArray ?

rsg_dj29-Jul-02 22:46

rsg_dj

29-Jul-02 22:46

<code></code>eg. How do I assign tc1.x = 20; in TestFunction2() ?

class TestClass1
{
public:
int x;
int y;
}

class TestClass2
{
public:
CArray<TestClass1, TestClass1&> arr;
}

void TestClass2::TestFunction1()
{
TestClass1 tc1;
for(int i=0; i<5; i++)
{
tc1.x = 5;
tc1.y = 10;
arr.Add(tc1);
}
}

void TestClass2::TestFunction2()
{
for(int i=0; i<tc1.GetSize(); i++)
{
tc1.x = 20; // does not work !!!
}
}

rsg_dj

arr.GetAt(...).x=20

Anonymous29-Jul-02 22:54

Anonymous

29-Jul-02 22:54

arr.GetAt(...).x=20

Re: How to change value of member within object within CArray ?

Alexandru Savescu29-Jul-02 23:34

Alexandru Savescu

29-Jul-02 23:34

GetAt will return a copy of the object, not the object itself.
Use ElementAt or operator[]

Best regards,
Alexandru Savescu

Re: How to change value of member within object within CArray ?

Raphael Kindt30-Jul-02 0:05

Raphael Kindt

30-Jul-02 0:05

You can use this:
SetAt(index, element);

Moreover, it's useful to use SetSize(size) for initializes the Array before using it. Frequent re-allocations thus are avoided...

Hello World!!! Smile | :)

from Raphaël

Re: How to change value of member within object within CArray ?

Alexandru Savescu30-Jul-02 0:31

Alexandru Savescu

30-Jul-02 0:31

Well, of course.

Moreover, it's better to use a std::vector don't you think?

Best regards,
Alexandru Savescu

Re: How to change value of member within object within CArray ?

Raphael Kindt30-Jul-02 1:06

Raphael Kindt

30-Jul-02 1:06

Really better... Wink | ;)

;);)

Hello World!!! Smile | :)

from Raphaël

Re: How to change value of member within object within CArray ?

Christian Graus30-Jul-02 2:47

Christian Graus

30-Jul-02 2:47

I know I'm a broken record in this topic, but assuming your question has already been answered, let me add that CArray is CRAP. You should do yourself a favour and read my STL series of articles, starting with the one on vector. Anyone who uses MFC container classes is using stuff written as a stopgap prior to the release of STL, and is selling themselves way short.

Read the articles and I am sure you will agree. CArray cannot do half of what vector does.

Christian

We're just observing the seasonal migration from VB to VC. Most of these birds will be killed by predators or will die of hunger. Only the best will survive - Tomasz Sowinski 29-07-2002 ( on the number of newbie posters in the VC forum )

Standard Radio Buttons

silverspoon29-Jul-02 22:10

silverspoon

29-Jul-02 22:10

I have the following trouble with !STANDARD! Radio Buttons:
I place 2 or more RadioButtons in Resource-Editor, I give the first element the group-flag via the property sheet and add one int variable to the first element. after that in InitDialog I do the following:
m_radioval = 1;
UpdateData(FALSE);
I get the following warning-messages in the output-window:
Warning: skipping non-radio button in group.

can anybody please explain me what happens? can't find anything on the net to that warning-message.
thanks in advance
silver

I don't want achieve immortality through my work - I want achieve it through not dying - Woody Allen

Re: Standard Radio Buttons

PJ Arends30-Jul-02 0:34

PJ Arends

30-Jul-02 0:34

All your radio buttons that you want grouped together have to be in the proper tab order, and the first control that comes after your group of radio buttons must have it's group flag set.

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