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I used a technique like that for one of my project, here is how it works (sorry, I don't have any link). You'll have to create a factory class that will manage the construction of the derived classes. This factory is basically a wrapper class around a map (the map link the name or the id of the inherited class and a function that is responsible of the creation of the class). So, when you want to create a class, you call a function from your factory (specifying the name or id, or...) of your class. The factory will then search in the map for the corresponding entry in the map and call the creation function (which is not part of the factory) and return the new instance.
So, as you can see, with this mechanism, you get rid of the switch logic.
Now, of course, your classes need to be registered with the factory. For that, in your factory add a method to register a class, by supplying the name or id of the class and a pointer to the creating function of the class (to keep it OO, this function can be a static function of your class). Like that, your objects can be registered in your factory, and be used anywhere in the code very easily.
The last point is really to register automatically these classes at the program start-up. To do that, you can use a little trick: define a static variable that is initialized by calling a function. This function will be responsible of registering your classes (static variables are evaluated before main gets called):
static int Var = RegisterMyClass();
The RegisterMyClass function will register the class in the factory.
So, in summary, what you have to provide when you want to add a new class: the class itself with a creation function (basically a simple new CMyClass), a function that will register the class (will simply call the Register of the factory and supply the class name and a pointer to the creation function) and a static variable that will only be used to register the class in the factory.
You can use a name to identify the class but you can also use an Id, it's up to you to decide what's the best option.
I hope this is clear. If not, don't hesitate to ask.
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I know of no way to accomplish this in C++, without COM, GUIDs and the like, but that could get ugly real fast. I think you're stuck with writing a class factory (google that) of some kind.
- S
50 cups of coffee and you know it's on!
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Hi All
Infact I learned from the page
http://www.sysinternals.com/Informa...plications.html
that applications can be run while booting by using native appliocations, here having one problem is that how to build a native application.
So please guide me to build the native application, I have windows 200
Professional .
Please guide me.
Thanks.
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any executable program can be run automatically while booting - not limited to "native app" (what does "native app" mean?).
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It is an application that uses The Native API[^]. Win32 sits on top of a "Native API". Programs like "chkdsk" which run before the system has fully booted use this API. To a large degree Win32 is implemented in terms of this API so it is more fundamental. For example the Win32 function CreateFile is really a wrapper around the Native API NtCreateFile function.
Steve
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I think you need the DDK to build native apps, but it's been a long time since I tinkered with that kind of thing.
Steve
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This is the first time I write a program after learning C++ for 1 week ago.
I use Dev-C++ and I want my program to do function such as:
Ask person to type two number : 1st number ; 2nd number.
such as: 2 ; 5;
and I want my program to get me the sum : 2 + 3 + 4 + 5 = 14
but I try many times and it always gives me : 2 + 5 = 7
This is my code :
using namespace std;
#include <iostream>
long result(long d , long e)
{
if (d >= 1 , d < e)
{
return (result(d + 1,0));
}
else
return (0);
}
int main()
{
long a,b;
long c;
cout << "1st number : ";
cin >> a;
cout << "2nd number : ";
cin >> b;
c = a + result(a , b) + b;
cout << c;
return 0;
}
Can someone tell what 's wrong with my code, and give me a hint to do it.
Thankz.
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simply write -
int main()
{
long a,b;
long c = 0;
cout << "1st number : ";
cin >> a;
cout << "2nd number : ";
cin >> b;
for (int i = a; i <= b; ++i)
c += i;
cout << c;
return 0;
}
your result() function is wrong which always returns zero.
Manish Agarwal
manish.k.agarwal @ gmail DOT com
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can you tell me why it is wrong and if i follow my way then what is the solution ?
By the way, thank you for your reply. This is my first time, seem that i have a lot of work to do.
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long result(long d , long e)
{
if (d >= 1 , d < e)
{
return (result(d + 1,0));
}
else
return (0);
}
this function is wrong because
result(d + 1,0) = 0 bacause d+1 > 0
if you replace e for 0: result(d + 1,0)->result(d + 1,e), this function still wrong because
result(d,e)=result(d+1,e)=.....=result(e,e)=0
-----------------
conglt
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if (d >= 1 , d < e) is legal syntax, but doesn't do what you want. Use && for "and" in boolean tests.
Look at your exit condition of result() - it only ever returns 0. Recursion is something you should really save for later, when you have more experience with the language.
--Mike--
Visual C++ MVP 
LINKS~! Ericahist | NEW!! PimpFish | CP SearchBar v3.0 | C++ Forum FAQ
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long result(long d , long e)
{
if (d >= 1 , d <= e)
{
return d + result(d+1,e);
}
else
return (0);
}
Instead of calling
c = a + result(a , b) + b;
only call
c = result(a,b);
Evaluation of recursive call is -
return 2 + result(2+1,5);
return 2 + 3 + result(3+1,5);
return 2 + 3 + 4 + result(4+1,5);
return 2 + 3 + 4 + 5 + result(6,5);
After if condition became false evaluation is
return 2 + 3 + 4 + 5 + 0;
return 2 + 3 + 4 + 5 ;
return 2 + 3 + 9;
return 2 + 12 ;
return 14 ;
In your code
long result(long d , long e)
{
if (d >= 1 , d < e)// After first iteration e became 0 and condition false and return 0;
{
return (result(d + 1,0));
}
else
return (0);
}
c = a+ result(a,b) + b = 2 + 0 + 5
Write recursive function carefully.
Regards
Amar
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are you student from Viet Nam ???
In your program :
you see again if statement:
if (d >= 1 , d < e)//or (d>=1 && d
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Thankz for all your reply.
I know my problem now.
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I am using the BackColor function, and all the documentation I have seen indicates that you have to let the user choose the color. I am wondering if there is a way to specify which color is used without the user choosing a color?
Thanks
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I'm not sure what "BackColor" function you're referring to or what parameter type it expects, but if it takes a COLORREF, you can make any color with the RGB macro or use any system colors with the GetSysColor() function.
COLORREF clr = RGB(255, 0, 0); // bright red
COLORREF clrWindow = ::GetSysColor(COLOR_WINDOW);
You might also need to use OleTranslateColor, if you're doing COM/OLE_COLOR related stuff.
- S
50 cups of coffee and you know it's on!
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Tried what you mentioned and it created many more problems that it solved.
The program began acting up and creating many errors with the MessageBox::Show function I am using.
Anyways, on second thought this should have gone in the managed forum but...
I am doing a System::Windows::Forms project, and changing the backcolor with this->BackColor. I have only found ways to let the user selectively change the color, but I would like to specify the color change myself. Do you know of a way to do this?
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Ahh, yeah, the code I mentioned probably wouldn't work in .NET, it's Win32 api.
I think you might need to look up the System::Drawing::Color class and do something like:
BackColor = Color::Red; (or whatever your color choice)
I'm not a .net expert, so hopefully the Color class has a constructor like Color(R, G, B) if you need to do an arbitrary color.
- S
50 cups of coffee and you know it's on!
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Steve Echols wrote: I think you might need to look up the System::Drawing::Color class and do something like:
BackColor = Color::Red; (or whatever your color choice)
Thanks. That worked. 
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Hello
I have a little problem with my app.
I can double click on the assotiated file type (*.app) an the MainFraim of my Prog is started. But to display the information in the file there should also be a ChildFrame opened. And this doesn't happen!
Now how to add this function ?
And/od how to debug this (if Possible)?
THX
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it is ur responsbility to open the file clicked.
check command-line of CWinApp then open a new Doc for the file.
A special image tool for C++ programmers, don't miss it!
The world unique Software Label Maker is here for you and me ...
A nice hyper tool for optimizing your MS html-help contents.
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hi guyss
I am in a grt problem. when i use installshield to build the setup file of my project, i follow all the steps required properly. after that the setup file is also created but when i install it neither it comes in the "all program". also when i install it in any other computer not having vc++ after installation when i click the exe file to run it gives an error of a missing dll file but i have included this dll file while making the setup. please help as soon as possible as i have to submit the project by a week.
Thanksss
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simanto_iem wrote: I am in a grt problem. when i use installshield to build the setup file of my project, i follow all the steps required properly. after that the setup file is also created but when i install it neither it comes in the "all program". also when i install it in any other computer not having vc++ after installation when i click the exe file to run it gives an error of a missing dll file but i have included this dll file while making the setup. please help as soon as possible as i have to submit the project by a week.Thankss
What exact is teh error Message.. if your Application is build in release mode!, as the debug mode dll may or may not be installed on destination computer
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
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Hi,
Does anyone know of a function that will allow me to distinguish between normal shell items like a text file or a folder & special items like MyComputer, shared documents folder, C drive, CD drive etc. In other words how do I get the attributes of these special folders.
Many thanks.
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Please refer to the shell programing section here in code project:
http://www.codeproject.com/shell/[^]
Ask not what your application can do for you,
Ask what you can do for your application
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