Question

Possible Duplicate:
How to create a Singleton in C ?

Hello, if I have a structure definition as follows:

struct singleton
{
    char sharedData[256];
};

Can I impose the singleton pattern on instance variables of the above structure in C [not in C++]?

Answer 1

If you just forward declare your struct in the header file, it will be impossible for clients to create an instance of it. Then you can provide a getter function for your single instance.

Something like this:

.h:

#ifndef FOO_H
#define FOO_H

struct singleton;

struct singleton* get_instance();

#endif

.c:

struct singleton
{
    char sharedData[256];
};

struct singleton* get_instance()
{
    static struct singleton* instance = NULL;

    if (instance == NULL)
    {
        //do initialization here
    }

    return instance;
}