how to call a class function from a static function

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how to call a class function from a static function

(9 posts) (5 voices)

Started 1 year ago by cocosboy
Latest reply from sndwav

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cocosboy
Member
Hi,

I am using this function to call a static function on collision of two objects in chipmunk.
```
cpSpaceAddCollisionHandler(space, 1, 2, CollisionFunction, NULL, NULL, NULL, NULL);
// I am using this line in init
```
static function that is called
```
static int CollisionFunction(cpArbiter *arb, cpSpace *space,  void *unused)
{
	cpShape *a, *b;
	cpArbiterGetShapes(arb, &a, &b);
        //[self MyFunction]; this line gives error that self is not defined
	return 1;
}
```
My static functions are defined in current class(inherited from CCLayer).
Now I wish to call a function in my Current class from this static function. when ever I write [self ....]. it says self is not defined.

any suggestion to call this function(MyFunction in above commented code).

thanks in advance
Posted 1 year ago #

crmagicxxx
Member

You should pass your class reference to that collision function, like this:

cpSpaceAddCollisionHandler(space, 1, 2, CollisionFunction, NULL, NULL, NULL, self);

That way you passed self to CollisionFunction. Now you can use it there:

static int CollisionFunction(cpArbiter *arb, cpSpace *space,  void *unused)
{
MyClassName *myClass = (MyClassName *)unused;

[myClass someMethodFromTheClass];

}

Where MyClassName is the name of that self you passed.

Posted 1 year ago #

cocosboy
Member

it works

thanks.

Posted 1 year ago #
bambamyi
Member

I did exactly the same thing, but I get an error saying "someMethodFromTheClass" may not respond error. Why am I getting this? Is it xcode setting or compiler setting?

Posted 1 year ago #
bambamyi
Member

ehh.. nevermind... I declared the method private... duh <.<

Posted 1 year ago #
sndwav
Member
sry to bump this up,
but I'm trying to do exactly what @crmagicxxx suggested,
and my app keeps crashing for some reason :/ I must be doing something wrong here.

my addCollisionHandler (in the HelloWorldScene.m)
```
cpSpaceAddCollisionHandler(space, 1, 2, playerCollision, NULL, NULL, NULL, self);
```
my handler (also in the HelloWorldScene.m)
```
static int playerCollision (cpArbiter *arb, cpSpace *space, void *data){
	cpShape *a, *b;
	cpArbiterGetShapes(arb, &a, &b);

	if (abs(a->body->v.y) > 260 || abs(a->body->v.x) > 260) {
		HelloWorld *game = (HelloWorld *) data;
		[game handlePlayerHP];
	}

	return 1;
}
```
my handlePlayerHP function, only with a NSLog for now
```
-(void) handlePlayerHP {
	NSLog(@"HP: %@",playerHP);
}
```
Can anyone explain to me what am I doing wrong here?
I don't get any compile errors whatsoever, but the app crashes on high impact.

When I just had a NSLog at that if statement, all worked well.

Thank you!
Posted 1 year ago #
Benihana
Member

HelloWorld *game = (HelloWorld *) data;

If you're passing "self" from a HelloWorldScene, why are you typing data as "HelloWorld" instead?

If you put a breakpoint at the first and second line of your if statement, which crashes your app? What does your log say when it crashes?

Posted 1 year ago #
crmagicxxx
Member
@sndwav I can't see error in your code (at least visually, I am not behind Mac to check it for sure). Only thing that comes up is
```
NSLog(@"HP: %@",playerHP);
```
Instead put simple NSLog(@"works") there and see. And if that works (as it should), trace your problem in playerHP

Best
Posted 1 year ago #
sndwav
Member

Now I feel silly :)

Thanks @crmagicxxx
I used %@ since I forgot the sign for NSLogging an integer (%d), and I thought that the NSLog Object is also a generic sign (since I thought anything can be considered an "object").
Won't happen again!

thanks!

Posted 1 year ago #

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