Re: c++ Factory pattern for large number of different classes. - C / C++ / MFC Discussion Boards

Richard MacCutchan31-Aug-09 4:08

31-Aug-09 4:08

Please see my previous message. You need to try and discover where the program is failing, and then examine the code in that area. Use the DEBUG mode and breakpoint facility to narrow the problem down. It is no good sending the complete code to me as I have no idea what the program is trying to do.

Make ActiveX have it's own thread

manchukuo28-Aug-09 17:41

manchukuo

28-Aug-09 17:41

Hi all!!

I am loading a swf file inside the ActiveX object in my dialog, but some operations inside the swf are lenghy and make my dialog not responsive, is there a way to make the Activex object run in an another thread?

Re: Make ActiveX have it's own thread

«_Superman_»30-Aug-09 21:24

«_Superman_»

30-Aug-09 21:24

You could make the lengthy operation run in a separate thread within the activex control.

«_Superman_»
I love work. It gives me something to do between weekends.

c++ Factory pattern for large number of different classes. (answered)

Maximilien28-Aug-09 10:09

Maximilien

28-Aug-09 10:09

(don't know if this should be in the design forum, anyway, I'm coding in C++)

I have a factory that will eventually create many, many different objects.

usually, I have something like (pseudo-c++-ish):

#include "type1Class.h"
#include "type2Class.h"
#include "type3Class.h"
#include "type4Class.h"

// typeXClass derive from BaseClass.
static BaseClass* MyClass::Builder(ObjectType type)
{
  switch (type)
  {
    case type1: return new Type1Class;
    case type2: return new Type2Class;
    case type3: return new Type3Class;
    case type4: return new Type4Class;
    //...
  }
}

Now, for a small number of classes this is manageable; but for a large number of classes it creates a large number
of includes and a huge switch.

Is there another pattern or methodology to clean that potential mess ?

I known I can put all typeXClass.h includes in a separate include file and have that one included; that will reduce the number of lines; any other tips hints ?

Thanks.

--------- edit------
Thanks to Stuart and Cédric; I will have a look at their solution first thing after coffee next monday!

This signature was proudly tested on animals.

Re: c++ Factory pattern for large number of different classes.

Garth J Lancaster28-Aug-09 14:26

Garth J Lancaster

28-Aug-09 14:26

Maximilien wrote:
Is there another pattern or methodology to clean that potential mess ?

I dont think so, but depends on your definition of large I guess - in which case you might want to partition your classes by some abstract case and have multiple factories.. you could also consider 'pre-allocating' the objects to trade off against the lookup time (if thats an issue) - we have an implementation in a realtime message-switch that only has 30-40 classes, one for each message, but we pre-allocate them in the factory before we start accepting connections

'g'

Re: c++ Factory pattern for large number of different classes.

Stuart Dootson28-Aug-09 14:27

Stuart Dootson

28-Aug-09 14:27

How would I do it...well, I'd make use of a std::map and some Boost magic:

struct BaseClass {};
struct C1 : public BaseClass {};
struct C2 : public BaseClass {};
struct C3 : public BaseClass {};

typedef BaseClass* BaseClassPtr;

BaseClassPtr Make(std::string const& type)
{
   using namespace boost::lambda;
   typedef boost::function<BaseClassPtr()> Constructor;
   static const std::map<std::string, boost::function<BaseClassPtr()> > factoryMap =
      boost::assign::map_list_of("C1", Constructor(new_ptr<C1>()))
                                ("C2", Constructor(new_ptr<C2>()))
                                ("C3", Constructor(new_ptr<C3>()));
   
   const std::map<std::string, boost::function<BaseClassPtr()> >::const_iterator constructor = factoryMap.find(type);   
   return (constructor != factoryMap.end())?constructor->second():0;
}

Create a map that relates your factory key to a suitable object pointer constructor function object - here I've used Boost.Lambda's object construction functions.

When you look up a type key, you either find it (in which case you invoke the constructor) or not (in which case I return a null pointer).

Adding a new type only requires you to add one line to the map initialiser.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: c++ Factory pattern for large number of different classes.

Maximilien29-Aug-09 3:10

Maximilien

29-Aug-09 3:10

hooooo!!! sexy!

Thanks.

This signature was proudly tested on animals.

Re: c++ Factory pattern for large number of different classes.

Cedric Moonen28-Aug-09 21:44

Cedric Moonen

28-Aug-09 21:44

I use an approach similar to the one from Stuart's but by using some little tricks, you can automate the process of registration.

So, the base principle is that the factory is aa wrapper around a map with the class identifier (type) as key and a function to create the object as value. So, this way your factory remains independant of your different objects.
Then, you have a public function on your factory to add a new creation function to the map:

// typedefinition of the creation function 
typedef BaseClass* CreateFunc ();

....
// In your factory:
void RegisterCreator(ObjectType type, CreateFunc* pFunc);

Now the "smart" trick is to let the classes register themselves through static initialization. At the top of the cpp file of your class, you add code similar to this:

int RegisterType1Class()
{
	CObjectFactory::GetInstance().RegisterCreator(Type1, Type1Class::CreateObject);
	return 0;
}
static int Temp = RegisterType1Class();

The Type1Class::CreateObjec is a static function of your class which simply creates a new instance of the class.

This mechanism allows you to automatically register objects to your factory through static initialization. Your factory has to be a singleton also.

Using this technique, your factory remains completely independant from all your different specific objects (it only has to know the base class), and you get rid of the big ugly switch.

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Re: c++ Factory pattern for large number of different classes. (answered)

Iain Clarke, Warrior Programmer29-Aug-09 5:42

Iain Clarke, Warrior Programmer

29-Aug-09 5:42

I know you already have answers...

But I'd look at this article, as I had a similar problem:
Enumerate your leaf classes[^]

This lets each class (inheriting froma common ancestor) register themselves, so it's all self contained. No adding a class in Pl;ace A, and not adding it to a list in place B.

Used it a few times myself.

Iain.

I have now moved to Sweden for love (awwww).
If you're in Scandinavia and want an MVP on the payroll (or happy with a remote worker), or need cotract work done, give me a job! http://cv.imcsoft.co.uk/[^]

2 questions of rich edit

includeh1028-Aug-09 10:03

includeh10

28-Aug-09 10:03

2 questions of rich edit control:

1. how to get last visible line - ref to function GetFirstVisibleLine(), or count of visible lines.

2. how to get line height of last line?

Re: 2 questions of rich edit

Code-o-mat29-Aug-09 1:41

Code-o-mat

29-Aug-09 1:41

1. You could try using CharFromPos[^] specifying the bottom-left corner of the edit and LineFromChar[^] to get the line index of the character it returned, if any. Maybe it would work, maybeit would not...
2. No idea just yet, sorry...

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Life: great graphics, but the gameplay sux. <

C/C++ code of Vernam Cipher Algorithm

Munna Bhagat28-Aug-09 6:44

Munna Bhagat

28-Aug-09 6:44

i need C code of Vernam Cipher Algorithm for my project work.plz help me .

Re: C/C++ code of Vernam Cipher Algorithm

CPallini28-Aug-09 7:02

CPallini

28-Aug-09 7:02

In your reposts, you're loosing words... Roll eyes | :rolleyes:

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: C/C++ code of Vernam Cipher Algorithm

Maximilien28-Aug-09 7:45

Maximilien

28-Aug-09 7:45

From what I can understand from a quick google, it looks like it's not a hard(*) thing to do.

-input XOR (randomly generated)mask = result.
-send result to receiver.
-result XOR mask = input.
-trash the mask.

(*) the difficulty would be to generate the random mask since generating truly random values is a very hard process.

What have you done already? did you do your homework and look at what this is ?
Did you try a few things ? do you have any workable code ?

This signature was proudly tested on animals.

Re: C/C++ code of Vernam Cipher Algorithm

Michael Schubert29-Aug-09 0:28

Michael Schubert

29-Aug-09 0:28

I think he only wantz da codez.

C/C++ code of Vernam Cipher Algorithm

Munna Bhagat28-Aug-09 6:41

Munna Bhagat

28-Aug-09 6:41

I need C or C++ code of Vernam Cipher Algorithm for my project work.plz help me soon.

C/C++ code of Vernam Cipher Algorithm

Munna Bhagat28-Aug-09 6:41

Munna Bhagat

28-Aug-09 6:41

I need C or C++ code of Vernam Cipher Algorithm for my project work.plz help me soon.

Anti virus live update corrupting file mapped shared memory

avijaya28-Aug-09 4:59

avijaya

28-Aug-09 4:59

My project compromises of a set of different process talking to each other. They communicate via file mapped shared memory. I ran into a problem when I was doing a symantec antivirus liveupdate when the different processes of our application starts behaving erratically.

I had to reboot to recover and then excluded the directory of my application and the shared page file from antivirus scanning.

Now all the processes of my application for some strange reason began crashing everyday midnight while accessing the shared memory. I managed to find that when some of these processes were configured to not use the shared memory, those processes didnt terminate.

Can anyone shed light on why this could be happening - esp why application went for a toss during the liveupdate. Is there any way/tools to debug crashes in the file mapped shared memory files??

Appreciate your help.

Re: Anti virus live update corrupting file mapped shared memory

Randor 28-Aug-09 6:09

Randor

28-Aug-09 6:09

Hi avijaya,

Is this behavior only occuring on Windows XP? Also... did you supply a SECURITY_ATTRIBUTES Structure[^] when creating the mapping?

Best Wishes,
-David Delaune

Re: Anti virus live update corrupting file mapped shared memory

avijaya28-Aug-09 6:15

avijaya

28-Aug-09 6:15

Hi David,

I did provide SECURITY ATTRIBUTES when I did CreateFile and CreateFileMapping. I gave a security descriptor that allowed anyone to access the object.

This problem is seen on Windows 2k3 Server.

-avijaya.

AfxDumpStack

Krishnakumartg28-Aug-09 3:35

Krishnakumartg

28-Aug-09 3:35

Friends,

void CAfxDumpStackDlg::Test()
{
	AfxDumpStack( AFX_STACK_DUMP_TARGET_ODS );
}

AfxDumpStack API call in the above code block dumps only the following information.

"=== begin AfxDumpStack output ===
Loaded 'C:\WINDOWS\system32\dbghelp.dll', no matching symbolic information found.
Loaded 'C:\WINDOWS\system32\version.dll', no matching symbolic information found.
7C90EB94: WINDOWS\system32\ntdll.dll! KiFastSystemCallRet
59A830F0: WINDOWS\system32\DBGHELP.dll! DbgHelpCreateUserDump + 331 bytes
=== end AfxDumpStack() output ==="

What should I do more to get the detailed dump?

Thanks in advance,
Krishnakumar

Re: AfxDumpStack

Randor 28-Aug-09 5:33

Randor

28-Aug-09 5:33

Krishnakumartg wrote:
What should I do more to get the detailed dump?

It appears that you need to setup your debug symbols.

How to use a symbol server with the Visual Studio .NET debugger[^]

INFO: How to Install the Debug Symbols for Use with Visual Studio Products[^]

Debugging Tools and Symbols: Getting Started[^]

Best Wishes,
-David Delaune

Re: AfxDumpStack

Krishnakumartg29-Aug-09 3:13

Krishnakumartg

29-Aug-09 3:13

thanks..let me check..

While Splitting the String* it throws Error....

spalanivel28-Aug-09 1:19

spalanivel

28-Aug-09 1:19

Hi,

In the strCommand I am having 2MB of Data and when i am trying to split with the new line it was throwing error.(to loop through all the data)

But it was working for minminum (ie 50 KB of datas like 0's and 1's).

How to over come this error? Very urgent.. Below is the code...

CString strCommand; // Holds 2MB of datas like 0's and 1's...

System::String* strDataReceived = "";
strDataReceived = strCommand;
__wchar_t split __gc[] = new __wchar_t __gc[1];
split [0] = '\n';
String *strSplitCommand[] = strDataReceived->Trim()->Split (split);

Please help..

Reg,
Subbu

Re: While Splitting the String* it throws Error....

CPallini28-Aug-09 1:41

CPallini

28-Aug-09 1:41

spalanivel wrote:
Very urgent..

It is so urgent to justify the cross-post [^]?
Smile | :)

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