C / C++ / MFC

11-Jan-06 23:33

void AFunction(void(*)())
{
   //i am innocent
}
//A class member function
void CAClass::AFunc()
{
    //I am getting an error...(it's given below)
    //is it wrong to do this
    //or can this be done in some other way.
    AFunction(this->AFunc);
}

error C2664: 'func' : cannot convert parameter 1 from 'void (void)' to 'void (__cdecl *)(void)'

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Prakash Nadar11-Jan-06 23:38

11-Jan-06 23:38

AFunc is a member variable, that is why youa re getting that error.

Can you consider making AFunc as static function?
or
check this[^]

-Prakash

Owner drawn11-Jan-06 23:41

11-Jan-06 23:41

Yeah it works with static, but why not with member functions. Sounds silly but still would like to know. Since it is also a function.

Edit:Thanks a lot prakash.

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Prakash Nadar12-Jan-06 0:07

12-Jan-06 0:07

Owner drawn wrote:
Sounds silly but still would like to know. Since it is also a function.

no its not silly, coz it has a good logic behind it, member function has a different "hidden" signature than other functions.

-Prakash

Owner drawn12-Jan-06 0:10

12-Jan-06 0:10

Mr.Prakash wrote:
no its not silly

Mr.Prakash wrote:
coz it has a good logic behind it, member function has a different "hidden" signature than other functions.

Yea you are right.

[Message Deleted]

Kedar Potdar12-Jan-06 0:30

Kedar Potdar

12-Jan-06 0:30

[Message Deleted]

Prakash Nadar12-Jan-06 0:32

12-Jan-06 0:32

kdar wrote:
The functions are mangled so that they can be uniquely identified and called upon invocation

no you are wrong. mangling is nothing to do with it. mangaling is more relevant for compilers and linkers.

The hidden param is the this param passed to the member functions.

-Prakash

Owner drawn12-Jan-06 0:35

12-Jan-06 0:35

kdar wrote:
The functions are mangled so that they can be uniquely identified and called upon invocation

~~How. Can you please elaborate. It would be helpful.~~

Edit:Where did he go Confused | :confused:

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-- modified at 6:47 Thursday 12th January, 2006

Prakash Nadar12-Jan-06 0:49

12-Jan-06 0:49

Owner drawn wrote:
Edit:Where did he go

he left coz he could not support his theory. Roll eyes | :rolleyes:

-Prakash

toxcct12-Jan-06 0:50

toxcct

12-Jan-06 0:50

Owner drawn wrote:
Edit:Where did he go

urgent need to go to the toilets !? Blush | :O

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Zzzz

Owner drawn12-Jan-06 0:56

12-Jan-06 0:56

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Re: Zzzz

ThatsAlok13-Jan-06 2:27

ThatsAlok

13-Jan-06 2:27

Owner drawn wrote:
ForumVisual C++
Subject:Re: Zzzz
Sender:Owner drawn
Date:6:56 12 Jan '06

don't sleep Smile | :)

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
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VC Forum Q&A :- I/ IV

Cedric Moonen11-Jan-06 23:45

Cedric Moonen

11-Jan-06 23:45

A function member of a class doesn't have the same prototype as a global function: there is the 'this' paramter that is passed as an implicit argument of the function (but it is transparent to the user). To avoid that, you can declare your member function as static. A static function is shared aming all instances of your class and thus doesn't require the implicit 'this' parameter. But of course, within a static function, you can only access static member of your class (because the function does not belong to a specific instance of the class).

Owner drawn11-Jan-06 23:48

11-Jan-06 23:48

Good. Well said.

Thanks a lot. Big Grin | :-D

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Blake Miller12-Jan-06 6:41

Blake Miller

12-Jan-06 6:41

within a static function, you can only access static member of your class (because the function does not belong to a specific instance of the class).

Unless you also pass a pointer to the object into the functiona as an additional argument, then you can access public members and functions of the class using the pointer to the class.

Marriage slows down your coding, a baby slows it down even more!

BadKarma11-Jan-06 23:57

BadKarma

11-Jan-06 23:57

Hi,

You can alsoo change AFunction to

void AFunction(void(CAClass::*pFunction)())
{
   //i am still innocent
}

this way you can pass a pointer to a member function.
This said you will need to have an object of the type CAClass available to execute the function.

codito ergo sum

Owner drawn11-Jan-06 23:58

11-Jan-06 23:58

Hmm...Cool Cool | :cool:

Nice one.

BadKarma wrote:
//i am still innocent

Now that's funny...He he Laugh | :laugh:

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C^hris L^osinger12-Jan-06 5:42

C^hris L^osinger

12-Jan-06 5:42

i use this macro:

// call mem fn that takes a single int
#define CALL_MEMBER_FN(object,ptrToMember)  ((object).*(ptrToMember)(int))

// fns have a single int param
typedef  void (CObjType::*fnType)(int); 

...

// holds a pointer to mem fn
fnType m_fnPtr;

...

// call it
CALL_MEMBER_FN(*this, fnPtr)(5);

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-- modified at 11:44 Thursday 12th January, 2006

Global Variable

<color>Aljechin 11-Jan-06 23:13

<color>Aljechin

11-Jan-06 23:13

1. I tried to use a global variable in every c++ file with the same name that is szRegPath (a CString). But I got some error and I had to use either different variable names in all the files (if global) or i had to put those inside functions. How can I resolve this?

2. I want to have one int variable which is global to all the c++ files and that should maintain its value state. If one file modifies the value to 7, then when it is called by another file, it should have its value as 7.

Please help me
Aljechin Alexander

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RChin11-Jan-06 23:28

RChin

11-Jan-06 23:28

Aljechin wrote:
I want to have one int variable which is global to all the c++ files

You would therefore need to declare your variable in a file that is visible to all your cpp files. I would suggest declaring it in your stdafx.h file, if using a standard mfc built application.

I Dream of Absolute Zero

<color>Aljechin 12-Jan-06 0:01

<color>Aljechin

12-Jan-06 0:01

Not just declaring. I need the variable to maintain its state throught the c++ files. How do i achieve this?

Thanks

Dennis Gourjii11-Jan-06 23:29

Dennis Gourjii

11-Jan-06 23:29

If you want those variables in different *.cpp files to be actually different variables and still compile, declare them as static (local to a particular *.cpp).

If, on the other hand, you need one variable to be global and available in several (or all) *.cpp files, do the following:
1) in some header: extern int myvar;
2) in any *.cpp: int myvar;
3) in every *.cpp where you need to use myvar: #include "that_header's_name.h"

<color>Aljechin 12-Jan-06 0:00

<color>Aljechin

12-Jan-06 0:00

HAND wrote:
1) in some header: extern int myvar;
2) in any *.cpp: int myvar;
3) in every *.cpp where you need to use myvar: #include "that_header's_name.h"

But this will become a local variable for every c++ file. I dont want that. I want a global variable with its state maintained throught all c++ files. How can I achieve this?