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There are two classes in my case, Class_A and Class_B. In Class_A.h, a Class_B member variable is declared. Hence, #include "Class_B.h" is put into Class_A.h. In Class_B.h, On the other hand, a Class_A member variable is declared. Hence, #include "Class_A.h" is put into Class_B.h.
However, the above arragement will cause C2146, C2501 errors. How to solve this dilemma.
Thanks,
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There's a couple of ways around the circular dependency problem:
a) Put your declarations in .h and put your definitions in .cpp.
b) Declare your classes, then in the same .h, put the definitions with the dependencies outside of the class.
a)
.h:
class Class_A;<br />
class Class_B;<br />
<br />
class Class_A<br />
{<br />
Class_B* _b;<br />
<br />
void func();<br />
};<br />
<br />
class Class_B<br />
{<br />
Class_A* _a;<br />
<br />
void func();<br />
};<br />
.cpp:
void Class_A::func()<br />
{<br />
_b->func();<br />
}<br />
<br />
void Class_B::func()<br />
{<br />
_a->func();<br />
}<br />
b)
.h:
class Class_A;<br />
class Class_B;<br />
<br />
class Class_A<br />
{<br />
Class_B* _b;<br />
<br />
void func();<br />
};<br />
<br />
class Class_B<br />
{<br />
Class_A* _a;<br />
<br />
void func();<br />
};<br />
<br />
<br />
void Class_A::func()<br />
{<br />
_b->func();<br />
}<br />
<br />
void Class_B::func()<br />
{<br />
_a->func();<br />
}<br />
In either case, the classes are declared, then the class functions are defined after they're declared.
-- modified at 2:31 Tuesday 7th November, 2006
- S
50 cups of coffee and you know it's on!
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You certainly meant Class_A* _a and Class_B* _b for the class declaration, no ? Otherwise, if you don't work with pointer this won't work.
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Oops! Yes. That's what I meant. My fingers got going a little too fast on the keyboard. 
Thanks!
- S
50 cups of coffee and you know it's on!
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I am a VC/MFC newbie. Why Class_A _a Class_B _b would cause errors. Why we cannot use them as we use 'int' 'float'. Would you please give more details.
Thank you.
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cy163@hotmail.com wrote: Why we cannot use them as we use 'int' 'float'
You don't need to 'define' what an integer is, do you ? Here, with classes, in order to use them, you need to first define them, that is provide all the members of the class (functions and variables). The compiler needs to compute the size of your class whenever you will use it in your code (to allocate memory for it). For that, all the members of the class needs to be known (and also need to know their respective size). If you include one object into a another and vice-versa, you cannot calculate the size, it's like in real life: try to put one container inside another one and then put the latter into the first one, quite tricky isn't it ? So, for the compiler it is the same.
Is you use pointers instead, that is different because a pointer is just an address (so a size of 4 bytes always).
cy163@hotmail.com wrote: I am a VC/MFC newbie
We all started there. But in this case, this is pure C++ (VC and MFC are microsoft and C++ is a standard language).
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Thank you Cederic,
and sorry, I still cannot understand. It is also possible to need to declare interge float type variables in a class, for example,
<br />
class Class_A<br />
{<br />
int i;<br />
<br />
void func();<br />
};<br />
<br />
OR
<br />
class Class_A<br />
{<br />
int *i;<br />
<br />
void func();<br />
};<br />
<br />
<br />
In the above examples, declarations 'int i' and 'int *i' are both ok.
For a Class_B type variable, why 'Class_B b" will cause problem, whereas 'Class_B *b" wouldn't.
-- modified at 18:24 Tuesday 7th November, 2006
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Yes, because in that case an integer is fully defined (you know its size and everything). In your case, if Class_A is declared before Class_B in the file and if it contains a Class_B has member, this Class_B has not been fully defined yet, so it is impossible for the compiler to create the Class_A.
Think of it as my example: try to put a box 1 inside another box 2 and then box 2 inside box 1. This is the same problem here. In the example with your integer, you simply put box 1 (the integer) into box 2 (your class) but your integer doesn't contain your class.
Another example: if you declared Class_A before Class_B in your example and if Class_A does't contain Class_B, then it would be ok:
Class_A
{
public:
Class_A();
~Class_A();
int Test;
};
Class_B
{
public:
Class_B();
~Class_B();
Class_A AnotherTest;
};
This will work because Class_A is fully defined when you use it in Class_B. Now, if you want to use Class_B inside Class_A you cannot do that directly (there is noway you can fully define both classes if they contain each other). The workaround is to use a pointer inside to Class_B inside Class_A: A pointer is always 'known' (its size is always 4 bytes). And you need to use forward declaration of Class_B (it is more or less the same as function prototype but for classes):
class Class_B;
Class_A
{
public:
Class_A();
~Class_A();
int Test;
Class_B* pB;
};
Class_B
{
public:
Class_B();
~Class_B();
Class_A AnotherTest;
};
Is it clearer now ?
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Cedric, I fully unstand the trick now.
Thank you very much.
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thank you Steve.
I forgot to say I am using MFC (visual C++ 6.0). In visual C++, a new class is implemented by a pair of files , *.h and *.cpp("Insert" | "Class" ....). Is it possible to mix two or more classes into one single file? Is it possible to merge two *.h files for two separate classes into single file and do the same thing with the corresponding *.cpp files?
-- modified at 18:34 Tuesday 7th November, 2006
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Hi friends
I developed a an address book program using CListCtrl. Contents of address book is more than 15000 entries. It causes slow while using address book. How can i solve this problem ? Kindly help me.
Thanks in advance
Regards
KK
KK
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Dont retrieve all addresses at one call only. Instead, Fill list control with number of empty rows equal to no. of records in address book. And then retrieve only records for rows visible in list control. Keep on retriving records on scrolling.
You can check if for this row records has been set to avoid multilpe calls.
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How do you insert your items to listctrl?
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If there isn't any frame in a html document,'elementFromPoint' would
work fine,but when the element is in a frame,'elementFromPoint' can not get it.
How can I get it in a frame?
Thanks!
3.141592653... Never Stop
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I have to place many check box on a Tab Page ,
but the checkbox have no caption ,
When the user want to slect any check box by
using the Tab switch on the keyboard. The checkbox
is not highlighted as it has no caption and He is
not able to identify the check box is currently slected
Can any one tell he some method trough which ,a higlight
or say a colour change can be done to the check box.
Remember we are not using the mouse (only keyboard)
thanks in advance
-- modified at 0:45 Tuesday 7th November, 2006
Vikas Amin
EATON
PUNE
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Why they dont have caption?
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I have lots of check box to be placed
on a small property sheet ,
more over grooping is possible so insted
of individual name groups have been created
Vikas Amin
EATON
PUNE
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First I have a suggestion if you dont have caption on checkboxs use of tooltip for them.For color my naswer is OwnerDraw I think you can find an example on codeproject for ownerdraw its three led (checkboxs).
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Owner-drawing the checkbox would probably be the way to go. There are plenty of articles on codeproject to guide you in owner-drawing controls.
I never thought of the fact that the focus indication is missing when omitting the label. Interesting.
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..coming to think of it, you could do your own bookkeeping of the focus in your dialog, and just draw the focus indication from your dialog class.
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I just have a dreadful feeling that your UI is going to suck.
Can you suggest a list control with the checkbox style, so all your items will fit on the window AND they can have labels?
Any sufficiently gross incompetence is nearly indistinguishable from malice.
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I am using this code to insert data in msaccess database,but rateher then saving the record it will save in database some otehr values:
like:
ID DateTimeStamp MarketNo Bid MarketName Ask MarketState
-858993459 0:00:00 0 -368934881474191.0324 -368934881474191.0324 -13108
-858993458 0:00:00 1342 -368934881474191.0324 -368934881474191.0324 -13108
-858993457 0:00:00 1342 -368934881474191.0324 -368934881474191.0324 -13108
-858993456 0:00:00 1342 -368934881474191.0324 -368934881474191.0324 -13108
-858993455 0:00:00 1342 -368934881474191.0324 -368934881474191.0324 -13108
How to solve this problem,I have made comment line before the database code by which i am getting this problem.
<br />
void CArielProjectVer2Dlg::OnPriceChangeArielapictrl1(LPCTSTR SessionId, LPCTSTR RequestId, short MarketNo, LPCTSTR Market,<br />
LPCTSTR Bid, short BidDirection, LPCTSTR Ask, short AskDirection, <br />
LPCTSTR High, LPCTSTR Low, short MarketState, LPCTSTR Timestamp) <br />
{<br />
SessID=SessionId;<br />
CurrentRequestId=RequestId;<br />
CString MarketSt,a,b,c,d;<br />
<br />
txtMarket = Market;<br />
<br />
a.Format("%d",MarketNo);<br />
b.Format("%c",BidDirection);<br />
c.Format("%c",AskDirection);<br />
d.Format("%d",MarketState);<br />
<br />
m_MainEdit=m_MainEdit + "<Price Change>" +" " + SessionId + "\t" + RequestId +"\t"+ a ; <br />
m_MainEdit=m_MainEdit + "\t"+ Market + "\t " + Bid + "\t " + b + " \t"+ Ask + "\t" +c +"\t "+ High + "\t";<br />
m_MainEdit=m_MainEdit + Low + "\t" + d + " "+ "\t" + Timestamp + "\r\n";<br />
<br />
UpdateData(FALSE);<br />
iLineCount=m_EditCtrl.GetLineCount();<br />
m_EditCtrl.LineScroll(iLineCount);<br />
<br />
<br />
m_TQuote.MoveLast();<br />
int nCount = m_TQuote.m_ID;<br />
nCount++;<br />
<br />
m_TQuote.m_ID = nCount;<br />
<br />
HRESULT hResult = m_TQuote.Insert();
if(FAILED(hResult))<br />
{<br />
AfxMessageBox(_T("Error inserting the record"));<br />
return;<br />
}<br />
-- modified at 22:44 Monday 6th November, 2006
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Hi,
could any body help, i want several techniques to hide a string from
debugging for example i need to hide lpszString_Tag from memory
LPCSTR lpszString_Tag = "CODEPROJECT";
...
MessageBox(lpzTitle,lpszString_Tag,MB_OK);
...
thanks
---
Anyone who considers arithmetical methods of producing random numbers is, of course, in a state of sin.
John von Neumann
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I assume you want to obfuscate the string so that it's not visible when greping through the binary for strings? You can always use XOR.
#define XOR_KEY "%¤#\"¤%!¤12323%%3kjlkjlkl5j312l4j3#¤\"!\"#"
int main(int ac, char** av) {
LPCSTR szKey = XOR_KEY;
int k = 0;
int s = 0;
printf("int len = %d;\n", strlen(av[0]));
printf("char str[] = { ");
while(av[0][s]) {
printf("%d", av[0][s] ^ *szKey++);
if(!*szKey)
szKey = XOR_KEY;
}
printf("};\n");
}This small app will from the first given program argument, generate an encoded char array, and a length variable containing the length of the array. The output may for example be:
int len = 6;
char str[] = { 5, 122, 53, 21, 45, 139 };In your app, include common.h, and put those variable declarations somewhere in your .cpp file. Then when you want to use the string, decode it using the XOR key again.
#include "common.h"
int len = 6;
char str[] = { 5, 122, 53, 21, 45, 139 };
...
LPCSTR newstr = new char[len + 1];
LPCSTR szKey = XOR_KEY;
for(int i = 0; i < len; ++i) {
newstr[i] = str[i] ^ *szKey++;
if(!*szKey)
szKey = XOR_KEY;
}
newstr[len] = 0;
At the end of this code, newstr will contain the string you passed as argument to the encoding application.
This encoding scheme works on the premise that: Charenc != Charorig ^ Key, and that Charorig = Charorig ^ Key ^ Key.
It won't help you against skilled crackers, but it will be a simple way to hide strings which you do not want to reveal for the casual "grepper".
--
Based on a True Story
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