callbacks in C?

MylesCLin · 02-09-2005, 10:23 PM

Hey, me again, still on Winblows.
I'm trying to, in C, have a pointer to a function in a structure.
So, for instance, struct object has a variable defined like so;

Code:

void *callback

and I would set this with a pointer to a function, then try and call the func like so;

Code:

items[1].callback();

The compiler complained about not being able to find the func, and then I fixed that, now it produces no errors, but the function doesn't print anything like it's supposed to.

Here's the code I have so far;

here's the item struct;

Code:

typedef struct item{
int location;
char name[20],desc[20];
void *callback;
} item;

Here's what configs the item;

Code:

void configitem(struct item *item,char name[20],char desc[50],int location,void *callback){
memcpy(item->desc, desc, strlen(desc));
memcpy(item->name, name, strlen(name));
item->location=location;
item->callback = callback;
}

and I call that like so;

Code:

configitem(&items[1],"Gun","A Gun",1,&poodle);

and here's how I'm calling the func;

Code:

items[1].callback;

Also, when I put parentheses around the callback that I'm trying to use, it says 'term does not evaluate to function'

MylesCLin · 02-09-2005, 10:43 PM

Whoops, resolved it.
I needed to create a function pointer.
A good resource is:
http://gethelp.devx.com/techtips/cpp.../10min0300.asp

Aga · 02-10-2005, 10:27 AM

define variable as
void (*callback)(); // pointer to function

not
void *callback; // void pointer