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hrishiS wrote: What does the code of default constrictor is...what I mean is what is the code present in the default constructor?
If you don't provide any constructor yourself, the default constructor will simply assign all variables, similarly as you would do something like this:
MyClass::MyClass(const MyClass& copy)
{
member1 = copy.member1;
member2 = copy.member2;
....
}
So, it means that if your class contains a pointer, this will result in something like this:
MyClass::MyClass(const MyClass& copy)
{
myPointer = copy.myPointer;
}
And of course this is not nice because both of your instances will have a pointer pointing at the same location and there's no way anymore to know which of the two has ownership of the pointer (so, which one is responsible for deleting it). And if you destroy that pointer in the class destructor, then you end up with the problem I described earlier: one instance will end up with a pointer pointing to memory which has been released (and thus which can contain corrupted data).
Furthermore, you can also encounter another problem than with the one you have when manipulating pointers. If one (or more) member of your class is an object that cannot be copied (because its copy constructor has been made private for instance), then your code won't even compile because there's no way for the default constructor of your class to copy the object (as the copy constructor is private). Thus, the only way to be able to copy your class is to provide a copy constructor that instead of calling the copy constuctor of your member, it will create an new instance of this member and initialize it properly.
hrishiS wrote: Could you please elaborate this, what exactly is meant by copying using shallow copy? Does this mean copying with the default copy constructor what we have?
It is assigning all members from one class to another as I described at the begining of this message.
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Cedric Moonen wrote: If you don't provide any constructor yourself, the default constructor will simply assign all variables,
But the default constructor doesn't have any parameter with it...So in that case to which value the member variable will get initialized to?...
Cedric Moonen wrote: It is assigning all members from one class to another as I described at the begining of this message.
Does it meant that shallow copy is member to member copying of each member variable one by one...?
is it,...Copy Constructor is doing shallow copy?
In that case, if we dont provide an copy constructor does the default copy constructor provides deep copy?
-----------------------------
I am a beginner
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hrishiS wrote: But the default constructor doesn't have any parameter with it...So in that case to which value the member variable will get initialized to?...
We are talking about the default copy constructor here. The default copy constructor receives the object from which to copy.
hrishiS wrote: Does it meant that shallow copy is member to member copying of each member variable one by one...?
is it,...Copy Constructor is doing shallow copy?
Yes, that's what I showed you in my previous reply: a default copy constructor simply assigns all members one by one (in fact, it is using the copy constructor of each member to create them and not the assignement operator, but this is not important in the discussion here). So, in that sense a default copy constructor is doing shallow copy.
hrishiS wrote: In that case, if we dont provide an copy constructor does the default copy constructor provides deep copy?
No, I just said the opposite: a default copy constructor does not make a deep copy. How could it do it ? You are the one how wrote the clas, so you know you have to copy some specific members (like pointers). The compiler doesn't know anything of that, he can simply assign all members from one object to the other. How can he know that for a pointer he has to allocate a new pointer and copy the content of the pointer ?
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I have an MDI application with CHtmlView. In CInvoiceHtmlView::OnBeforeNavigate2(...)I see if a special button is pressed. When is pressed , I would like to close child frame , but I don't know where I do that ...
Here is my trials :
<br />
void CInvoiceHtmlView::OnBeforeNavigate2(LPCTSTR lpszURL, DWORD nFlags, LPCTSTR lpszTargetFrameName, CByteArray& baPostedData, LPCTSTR lpszHeaders, BOOL* pbCancel) <br />
{<br />
<br />
if(m_bProcessNavigate)
{<br />
CString sBytes;<br />
<br />
if(baPostedData.GetSize())<br />
{<br />
for(int i = 0;i < baPostedData.GetSize();i++)sBytes += (char)baPostedData[i];<br />
}<br />
<br />
sBytes = sBytes.Left(7);<br />
if(sBytes == "button2")m_bClose = TRUE;<br />
}<br />
<br />
CHtmlView::OnBeforeNavigate2(lpszURL, nFlags, lpszTargetFrameName, baPostedData, lpszHeaders, pbCancel);<br />
}<br />
now : m_bClose show me if special button was fired , but I don't know how can I use this to close child window ...
modified on Friday, December 4, 2009 4:51 AM
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as we know, we can share the same memory in multi-processes through dll-library. if i use stl container as the public accessing memory in multi-processes, does it could do effect, thanks.
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What is a point? How do you want to write down as codes?
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norish wrote: What is a point?
A point is an entity that has a location in space or on a plane, but has no extent.
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thank you, i had tried and it can't do.
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Hi Friends,
How can I Access CDialog Class Member Variables in CDocument Class For Some Process...i Tried a lot..but it give error..plz gve me a solution .. 
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What is the relationship between the CDocument and CDialog classes in your project?
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kamalilam wrote: Access CDialog Class Member Variables in CDocument Class
If the member variables are declared as Public, use it directly from the object of the dialog class.
For e.g ,
CDocument* pDoc;
pDoc->m_oDialog.m_nMember1 = 10;
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The same way you would do for any other classes. Your CDialog and CDocument classes are still classes and they follow the same rules as normal classes. So, to be able to access a variable from a CDialog object, you first need to have an instance of that class (e.g. CDialog myDialog, in which case myDialog is your instance). Then your CDocument needs to be able to access that variable (if he create the instance, then he already owns it and can use it). Finally, the members you want to access in your dialog class have to be accessible, which means either they are public or you provide a getter method for them.
But this is really basic C++ knowledge, I suggest you take some time to read and understand the concept of classes, because that's exactly what it is here. It's not because those classes are document and dialog classes that they do not follow the standard rules of C++.
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Will you please include some relevant information in your post?
Are the CDialog members you're talking about public? How is this CDialog object related to the CDocument object in your application?
kamalilam wrote: Tried a lot..but it give error.
*What* did you try and *what* were the errors for Chri' sake?
“Follow your bliss.” – Joseph Campbell
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I have to return the path of the selected file , EITHER in the Desktop or in the Windows Explorer.
I can get the path of the selected file both on the Windows Explorer and the desktop
My problem is that I am unable to find which window has the current focus
1) The user has selected a file on the desktop
2) The user has selected a file in the Windows explorer. ( So this has the focus now )
How do I programatically find that out
I am using the following code
HWND hWndDesktop = GetDesktopHandle(); // Gets the handle of the SyslistView32 window
DWORD dwThread = ::GetWindowThreadProcessId(hWndDesktop, NULL);
GUITHREADINFO gtf ;
gtf.cbSize = sizeof(GUITHREADINFO);
BOOL b = GetGUIThreadInfo(dwThread, >f);
if(hWndDesktop == gtf.hwndFocus)
{
// this window currently has the focus
}
But I am getting different handles for hWndDesktop and gtf.hwndFocus .
Please let me know if I am missing something
EDIT
I am trying to get the Window handle across processes .
Thanks
Sujay
modified on Friday, December 4, 2009 12:40 AM
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Use GetFocus to get the handle to the window that has the focus.
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HI ,
GetFocus does return me the correct window handle also.
I had tried with GetFoucs,GetActiveWindow, none of them are working
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Superman, Does the GetTopWindow help in this regard ?
Or, What about using File Change Notification[^] to get the changes user made in file system ? Not sure these are relevant for the OP.
modified on Friday, December 4, 2009 1:37 AM
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i have tried what u have done .
that GetFocus function is retirning is NULL when iam calling in thread.
so, that i tried one more function GetForegroundWindow();
this also returns HWND.
CWnd *wnd=NULL;
HWND hWnd = NULL;
CString strwndName;
while (1)
{
hWnd=::GetFocus();
if(hWnd==NULL)
hWnd=GetForegroundWindow();
GetWindowText(hWnd,strwndName.GetBuffer(),20);
dlg->m_ed1.SetWindowText(strwndName);
}
just try it.. it will be work...
Regards,
Srinivas
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Hi,
I'm using VS 2005 and MFC, and I want to modify a system environment variable. So I looked up in the MSDN help and found that it is easy to set a user environment variable. However, for changing a system variable, the help says:
"Calling SetEnvironmentVariable has no effect on the system environment variables. The user can add or modify system environment variables using the Control Panel. To programmatically add or modify system environment variables, add them to the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment registry key, then broadcast a WM_SETTINGCHANGE message. This allows applications, such as the shell, to pick up your updates. Note that environment variables listed in this key are limited to 1024 characters."
I understand that, but find this way very error-prone and complicated. Is there really no easy, straightforward way to do such a simple thing as setting a system variable? No other methods availbale in MFC?
Thanks alot
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That is a better method than I am aware of. I typically modify the registry via code and reboot the computer when necessary.
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Thanks alot, I have now implemented it that way, and I also send the message this way that the environment has changed:
int nVal = SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE,0,(LPARAM)(_T("Environment")),SMTO_BLOCK | SMTO_ABORTIFHUNG | SMTO_NOTIMEOUTIFNOTHUNG, 5000, &dwReturnValue);
That works for all other processes, i.e. all the other processes that I start after I sent this message know the newly created system variable, and I do not have to restart my system.
However, the process that is currently running, i.e. the process that I used to set this variable is NOT aware of it, so if I make a call to GetEnvironmentVariable after setting it, I do NOT get it. I only get it if I restart the process.
is there a way to know that variable in the same process right after it has been created?
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Erik wrote: is there a way to know that variable in the same process right after it has been created?
Is it responding to the WM_SETTINGCHANGE message?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
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use DDK, build resource file (only a ICO file) , but sys file( or res file ) contain "c:\sample\resouce\sample.ico" strings, why ? how to remove it? thanks.
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It is path of the resource in local machine.
res file is intermediate file so wont be a problem just refer [^]
It wont be problem as far as i know.
Величие не Бога может быть недооценена.
modified on Friday, December 4, 2009 12:03 AM
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