c++ and using public static members in a class

Alan Kurlansky

How do you do a extern type declaration for this. At link time I get unresolved external symbol "public: static void__cdecl etc. etc. I'm trying to expand my use of C++ to envelop static functions inside of classes as a way to help organize the code a bit better.

Chris Losinger

this worked for me:

class A
{
public:
static void g(int)
{
int i = 0;
}
};

typedef void (*fp)(int);

int _tmain(int argc, _TCHAR* argv[])
{
fp p = A::g;
p(1);
return 0;
}

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Alain Rist

// MyClass.h
class MyClass
{
static INT m_i;
// ...
};
// if you want to keep it in definition part
__declspec(selectany) INT MyClass::m_i; // default initialized to 0

or

// MyClass.cpp
// ...
// if you want to have it in implementation part
INT MyClass::m_i; // default initialized to 0
// ...

cheers, AR

When the wise person points at the moon the fool looks at the finger (Chinese proverb)

Avi Berger

Static member functions usage: MyClass.h:

class MyClass
{
public:
static int fcn( int param );
static int inlineFcn( int param) ) // may be inlined, but not guaranteed
{
// just a little stuff
};
};

MyClass.cpp:

#include "Myclass.h"

int MyClass::fcn( int param )
{
// stuff
}

Client.cpp:

#include "Myclass.h"

void clientFcn( int a, int b )
{
// stuff

int c = MyClass::fcn( a );
int d = MyClass::inlineFcn( b );

// more stuff

}

It sounds to me that another approach might be more suitable for your purposes. I'll post that next.

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Avi Berger

Alan Kurlansky wrote:

a way to help organize the code a bit better

It sounds to me like you want the organization, but what you are doing is not truly about classes and object orientation. There is another facility in C++, namespaces, that may be more appropriate for your current use. It organizes things in groups and helps avoid naming conflicts, but does not raise the "object" expectations of someone reading your code. In some ways using namespaces looks a lot like what I posted for static member functions. This is how you might use namespaces: Group.h:

namespace Group
{
int fcn( int param );
inline int inlineFcn( int param) ) // may be inlined, but not guaranteed
{
// just a little stuff
};
}

Group.cpp:

#include "Group.h"

namespace Group
{
int fcn( int param )
{
// stuff
}
}

Client.cpp:

#include "Group.h"

void clientFcn( int a, int b )
{
// stuff

int c = Group::fcn( a );
int d = Group::inlineFcn( b );

// more stuff

}

AlternateClient.cpp:

#include "Group.h"

using namespace Group;

void altClientFcn( int a, int b )
{
// stuff

int c = fcn( a );
int d = inlineFcn( b );

// more stuff

}

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Alan Kurlansky

Yes, organization is what I'm looking to do in this case. This looks good. I'll give this a try. Thanks

Alan Kurlansky

Thanks. This looks good. I'll give it a try.

Avi Berger

Good luck. I hope it works well for you. I will add a note about style. My example showed indenting a level inside the namespace definitions, just like you would do for any other pair of {}'s. There are style guidelines that recommend not doing so for namespaces. I'm undecided about this myself.

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