Using iterateFunc to call objective c method

Question

Using spacemanager, I need to perform an action on select bodies after each step, so I figured that defining my own C function for iterateFunc would be the way to go.

Everything works great, except I'm not sure how to then call an obj c method in the same class. In other words, an obj c class contains both the c function replacing iterateFunc, and the method that needs to be called. I don't see how to tell the c function what 'self' is, such that I can call the method. As far as i can tell, there's no way to pass in any extra info to the new iterateFunc.

Any ideas, or a better way to go about things?

Answer 1

Holy vagueness, batman, where's the code snippet? Thankfully, the Magic Powers of Google save the day.

To answer this question requires a few bits of detail:

What is the declaration of iterateFunc?

Oh. It is a cpSpaceHashIterator. Not helpful.

Ah... there it is:

typedef void (*cpSpaceHashIterator)(void *obj, void *data);

It looks like the void *data argument is your answer. Specifically, it looks like that is passed through transparently to your iterator function. That is, if you call:

cpSpaceEachBody(cpSpace *space, cpSpaceBodyIterator func, void *data)

Like this:

cpSpaceEachBody(space, funcPtr, (void *)self);

Then your iterator func could do this:

void iteratorFunc(void *obj, void *data) {
    [(MyClass *)data iterateThis: obj];
}

Answer 2

Thx for the response. Declaring a new spacemanager, one can redefine its iterateFunc:

smgr = [[SpaceManager alloc] init];
smgr.iterateFunc=doThisFunc;

In the same class, a "doThisFunc" function can be declared.

In spacemanager, this "iterateFunc" is called from the "step" method:

 -(void) step: (cpFloat) delta
{
.....
    cpSpaceHashEach(_space->activeShapes, _iterateFunc, self);
....
}

So my first thought was to subclass spacemanager, and in my custom step method, call cpSpaceHashEach with my own class, instead of self (the spacemanager, that is). Halfway there, I realized that I didn't even have to do that, as subclassing and defining my own step method was all I needed to do. My new step method:

-(void) step: (cpFloat) delta
{       
    [super step:delta];
    [myObject doThis]; //Having of course set the "myObject" variable elsewhere as my other object
}

Thanks, bbum for both your answers, and for helping me craft better questions in the future.