C / C++ / MFC

31-Jul-03 4:00

Hi all
Can i get some way to retrieving pointer on member function of my class i.e. make like this

<br />
class A{<br />
   void Fun(){<br />
     void *pF = &this->Fun;<br />
  }<br />
}<br />

By compiled this snippet, compiler complain:
illegal operation on bound member function expression

Whether exit way what i can do it???
Thanks
Sorry for bad eanglish

Mike Dimmick31-Jul-03 4:44

Mike Dimmick

31-Jul-03 4:44

Do you mean, 'how can I get something which represents the combination of an object and a member function'?

You can do this with the STL using the mem_fun_t template. The language itself does not permit such an operation. The expression this->Fun is considered to be a bound member function - the only thing you can do with such an expression is to use the () operator on it (i.e., call it).

El'Cachubrey31-Jul-03 23:19

31-Jul-03 23:19

Thanks for advice but whats a reason which prevent do this???

Ryan Binns31-Jul-03 5:32

Ryan Binns

31-Jul-03 5:32

You can do this, but the syntax is slightly different:

void (A::*pF)() = A::Fun;

You will have to call the function in the context of an object:

A obj;
(pobj.*pF)();
A *pobj = new A;
(pobj->*pF)();

Hope this helps,

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

El'Cachubrey31-Jul-03 23:27

31-Jul-03 23:27

Hi I apparently cant properly realise you because of code dont
wont work by me.

Please see this code and ask where i wrong :

class A{

void Fun(){}

void CallFun(){
  void (A::*pF) () = A::Fun;
}

}

//Linker show error:
error C2440: 'initializing' : cannot convert from 'int' to 'void (__thiscall A::*)(void)'
There are no conversions from integral values to pointer-to-member values
Thanks

El'Cachubrey31-Jul-03 23:30

31-Jul-03 23:30

Hi I apparently cant properly realise you because of code dont
wont work by me.

Please see this code and say where i wrong :

class A{

void Fun(){}

void CallFun(){
  void (A::*pF) () = A::Fun;
}

}

//Linker show error:
error C2440: 'initializing' : cannot convert from 'int' to 'void (__thiscall A::*)(void)'
There are no conversions from integral values to pointer-to-member values
Thanks

Ryan Binns31-Jul-03 23:39

Ryan Binns

31-Jul-03 23:39

Strange... Your code compiled perfectly with my compiler, and so did the code I provided. Instead of assigning A::Fun you can try using just Fun, but it should work anyway.

What version of VC are you using?

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

El'Cachubrey1-Aug-03 3:10

1-Aug-03 3:10

OOps
Excuse this warm make me completly dump
I forget set semicolon after class brace!!!
Now all fine.
Very thanks. WTF | :WTF:

Ken Mazaika31-Jul-03 6:35

Ken Mazaika

31-Jul-03 6:35

This page[^] might help you out.

Alexander ^M.,31-Jul-03 10:35

Alexander ^M.,

31-Jul-03 10:35

lol, what joky answers here... Cool | :cool:

define the member function static and there shouldn't be a problem anymore

Don't try it, just do it! Wink | ;-)

Check existance of directory

Mike Dimmick31-Jul-03 23:48

Mike Dimmick

31-Jul-03 23:48

I think we were all assuming that the original poster needed the function to be a member function ('instance method' in C# terminology).

A static member function has no this pointer, of course.

OK, you can do hacks like passing a pointer to the object into the static member function as a parameter, but that doesn't really gain you anything. I only ever do this when creating a thread or writing a callback function for interfacing with a C API - this type of function usually gives you a void* or LPARAM parameter which you can pass arbitrary data in, which gets passed to your thread entry point or callback function.

BoudewijnEctor31-Jul-03 3:59

BoudewijnEctor

31-Jul-03 3:59

Does anyone have the MFC equivalent of

directory.exists()?

Brian Shifrin31-Jul-03 4:03

Brian Shifrin

31-Jul-03 4:03

How about GetFileAttributes(file)
and check for FILE_ATTRIBUTE_DIRECTORY ?

valikac31-Jul-03 6:10

valikac

31-Jul-03 6:10

One solution is FindFirstFile() and FindNextFile().

Kuphryn

Joel Lucsy31-Jul-03 7:31

Joel Lucsy

31-Jul-03 7:31

Or how about CFile::GetStatus

Joel Lucsy

Toni7831-Jul-03 18:55

Toni78

31-Jul-03 18:55

Or you could use SetCurrentDirectory(). If the function returns FALSE then the directory doesn't exist. You should also call GetLastError() and make sure that it returns ERROR_PATH_NOT_FOUND (I am not sure if that's the actual error but you can figure that out), because there could be several reasons why SetCurrentDirectory() might return FALSE. (make sure you save the current directory before calling the function, in case the directory you are seaching for exists).

// Afterall, I realized that even my comment lines have bugs

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