Re: How do I do this? - C / C++ / MFC Discussion Boards

Anonymous1-Oct-02 9:31

1-Oct-02 9:31

I defined 2 classes - A and B;

class A {
public:
B GetB() {
return B();
}
};

class B {
public:
A GetA() {
return A();
}
};

since both classes make use of eachother, i get an "error C2501: 'A::B' : missing storage-class or type specifiers" when I try to compile.

Is this sort of thing supported with C++?

Re: How do I do this?

Nick Parker1-Oct-02 9:40

Nick Parker

1-Oct-02 9:40

Someone else may give a better example but this is possible through inheritance.

class A
{
protected:
   int Age;
   int GetAge()
   {
      return Age;
   }
};

class B:A
{
 int f;
 void Foo(); 

};

Access to the variable Age is available as B inherits A

//===========
B b;
b::A.Age;

Nick Parker

The goal of Computer Science is to build something that will last at least until we've finished building it. - Unknown

Re: How do I do this?

Scott H. Settlemier1-Oct-02 9:51

Scott H. Settlemier

1-Oct-02 9:51

use a forward declaration:

class B;

class A
{
public:
   B GetB();
};

class B
{
public:
   A GetA();
};

and put implementation in the .cpp file

Re: How do I do this?

Michael Dunn1-Oct-02 9:47

Michael Dunn

1-Oct-02 9:47

The class B isn't defined at the point you're trying to use it:

class A {
public:
  B GetB() { return B(); } <font color=red>// class B not defined here</font>
};

thus you get the error. Add a forward declaration of B so the compiler knows what it is:

class B; // forward declaration
 
class A { ...

--Mike--
Just released - 1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click!
My really out-of-date homepage
Sonork-100.19012 Acid_Helm

Re: How do I do this?

PJ Arends1-Oct-02 9:47

PJ Arends

1-Oct-02 9:47

use a forward declaration of class B.

class B; // forward declaration

class A
{
public:
    B GetB() {
...
}

class B
{
   A GetA () {
...
}

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: How do I do this?

Mariusz Popiolek1-Oct-02 9:52

Mariusz Popiolek

1-Oct-02 9:52

At the point where you define class A compiler knows nothing about identifier B, that's why error occurs. Put this before declaration of A:
class B;
Now compiler knows that B is a class, but that's not all. To return B from function compiler must know declaration of B, so you have to return pointer to B, not object B(when compiler see pointer to class, it doesn't have to know declaration of this class). Also you can't call constructor of B at this point, so just declare function in a class A and make a definition after a declaration of class B.

Greetings
Mariusz Popiolek

Re: How do I do this?

Scott H. Settlemier1-Oct-02 10:00

Scott H. Settlemier

1-Oct-02 10:00

LOL!

It's like a whole class full raising their
hands all at once 'cause it's one of the
answers everyone has just waiting for an
opportunity to get out.

Re: How do I do this?

PJ Arends1-Oct-02 10:15

PJ Arends

1-Oct-02 10:15

Yeah well, what can I say. It was an easy question and I need to get my post count up a little Big Grin | :-D

Re: How do I do this?

Mariusz Popiolek1-Oct-02 10:15

Mariusz Popiolek

1-Oct-02 10:15

When I have seen this question there wasn't any answers, but when I finished answering the post(I tried the code in VC to be sure if it's working), there was already plenty of answers Smile | :)

.

Greetings
Mariusz Popiolek

Re: How do I do this?

Roger Stewart1-Oct-02 10:00

Roger Stewart

1-Oct-02 10:00

To avoid this error, you can 'forward declare' class B.

class B;

class A
{
public:
   B GetB() { return B(); }
};

class B
{
public:
   A GetA() { return A(); }
};

Roger Stewart
"I Owe, I Owe, it's off to work I go..."

Re: How do I do this?

Anonymous1-Oct-02 11:05

Anonymous

1-Oct-02 11:05

thanks every one

clistctrl::getitmeText

pnpfriend1-Oct-02 9:07

pnpfriend

1-Oct-02 9:07

I have listctrl with rows(vary) and 3 column
let say first column is a,second is b, third is c;
I want the data of a, b, and c of the row.
so i tried the following ways

<br />
for(int i=0;i<numberOfRow;i++) //<br />
{<br />
CString dataA = myListCtrl.GetItemText(i,0);<br />
CString dataB = myListCtrl.GetItemText(i,1);<br />
CString dataC = myListCtrl.GetItemText(i,2);<br />
<br />
// anothe method<br />
LV_ITEM lvitem;<br />
ZeroMemory(&lvitem, sizeof(lvitem));<br />
lvitem.mask = LVIF_TEXT | LVIF_STATE;<br />
lvitem.iItem = nIndex[i]; <br />
lvitem.iSubItem = 1; <br />
myListCtrl.GetItem(&lvitem); <br />
<br />
dataA = lvitem.pszText;<br />
}<br />

both ways gave me let say dataA value as junk. How can I get back my item text???

Thanks

Re: clistctrl::getitmeText

Michael Dunn1-Oct-02 9:50

Michael Dunn

1-Oct-02 9:50

Can't say why the first way is failing, but the second doesn't work because you're not providing a buffer for the control to store the text in. You need to set pszText and cchTextMax to the address and size of the buffer before calling GetItem().

--Mike--
Just released - 1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click!
My really out-of-date homepage
Sonork-100.19012 Acid_Helm

Re: clistctrl::getitmeText

pnpfriend2-Oct-02 5:43

pnpfriend

2-Oct-02 5:43

let me try
Thanks Michael

how to give the catch block a filename?

ns1-Oct-02 9:06

1-Oct-02 9:06

If theres a problem with file strFile0 and an exception is thrown, I want the error message to have the name of the faulty file. This name is gotten in the try block. I dont think I can pass it in the catch argument:

catch(CFileException e, strFile0)
		
		{

			CString temp;

			temp.Format("Error opening file  : %d", e.m_cause);
			AfxMessageBox(temp);

			return -1;
		}
}

So how do I communicate it to my messagebox in the catch block?

Appreciate your help,
ns

Re: how to give the catch block a filename?

jmkhael1-Oct-02 9:08

jmkhael

1-Oct-02 9:08

catch(CFileException e, strFile0)

{

CString temp;

temp.Format("Error opening file : %d ", e.m_cause);
AfxMessageBox(temp + e.m_strFileName);

return -1;
}

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

Re: how to give the catch block a filename?

ns1-Oct-02 9:13

1-Oct-02 9:13

Thats convenient! You did however mean to remove the strFile0 argument I was trying to pass in, right ? I am off to look up CFileException and see what all it exposes... Smile | :)

Many thanks,

Appreciate your help,
ns

Re: how to give the catch block a filename?

jmkhael1-Oct-02 9:14

jmkhael

1-Oct-02 9:14

Yeah that way, i mean if u correct ur own mistakes u wont ever make them again Smile | :)

For ur own good (ok, i forgot Smile | :)

)

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

Re: how to give the catch block a filename?

Tomasz Sowinski1-Oct-02 11:29

Tomasz Sowinski

1-Oct-02 11:29

CFileException has m_strFileName member which contains file name.

Tomasz Sowinski -- http://www.shooltz.com

*** Si fractum non sit, noli id reficere. ***

Remote Library Access

Anonymous1-Oct-02 8:52

Anonymous

1-Oct-02 8:52

Is it possible to perform development in Visual Studio by having the libraries of a third-party component on a remote machine?

Any suggestions?!

Re: Remote Library Access

Daniel Lohmann1-Oct-02 9:56

Daniel Lohmann

1-Oct-02 9:56

Aehm, add the path to the library folder on the remote machine to your LIB path?

--

Daniel Lohmann

http://www.losoft.de
(Hey, this page is worth looking! You can find some free and handy NT tools there Big Grin | :-D

)

Displaying data from memory in an SDI application

johann_malherbe1-Oct-02 8:53

johann_malherbe

1-Oct-02 8:53

I have read data from a database into memory using a dinamic linked list in an SDI appication. Now I want to display the data, but I am having trouble doing so.

Re: Displaying data from memory in an SDI application

jmkhael1-Oct-02 9:06

jmkhael

1-Oct-02 9:06

http://www.codeproject.com/library/gridprojects.asp

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

Stream Design

Davy Mitchell1-Oct-02 8:35

Davy Mitchell

1-Oct-02 8:35

Hello,

If an ostream is open and a write operation completed, then a flush called, is the data 100% committed to disk or is there a delay?

Cheers,

Davy

Weblog, Ramblings and more...
www.latedecember.com

Re: Stream Design

Joaquín M López Muñoz1-Oct-02 10:06

Joaquín M López Muñoz

1-Oct-02 10:06

The data is 100% commited to disk.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

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