How to reference the SKSpriteNode that's running an SKAction runblock? - objective-c-blocks

Question

I have a method that creates a random amount of SKSpriteNodes that are supposed to fall from the roof, sit on the ground a little while, then fade out. They need an SKPhysicsBody so they'll fall and bounce properly, but when I create a lot, it's using a lot of CPU, so I was trying to remove their physicsbody when they'd been sitting on the ground a little while.
I can't figure out how to use a runBlock to just say "do (blah) to the object calling this runBlock", is there a way?
for (int i=0; i < howManyDollars; i++) {
SKSpriteNode *bills = [SKSpriteNode spriteNodeWithImageNamed:#"bills.png"];
int startX = arc4random() % (int)self.size.width/3;
int startY = self.size.height;
bills.position = CGPointMake(startX, startY);
bills.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:CGSizeMake(bills.size.width/2, bills.size.height/2)];
bills.physicsBody.affectedByGravity = YES;
[self addChild:bills];
SKAction *wait1 = [SKAction waitForDuration:1.5];
SKAction *wait2 = [SKAction waitForDuration:2];
SKAction *removeDynamics = [SKAction runBlock:^(void) {
// this is the spot I am confused at.
//bills.physicsBody = nil;
}];
SKAction *fade = [SKAction fadeOutWithDuration:15];
SKAction *remove = [SKAction removeFromParent];
[bills runAction:[SKAction sequence:#[wait1, removeDynamics, wait2, fade, remove]]];
}

Answer 1

You have it already:
SKAction *removeDynamics = [SKAction runBlock:^(void) {
bills.physicsBody = nil;
NSLog(#"bills is: %# (%p)", bills, bills);
}];
The cool thing about blocks is that they retain (copy) the objects in local scope. So if you create a block like the above and dereference the bills object, then for each block it will use the corresponding bills object that runs the action.
I've added the log statement so you can see for yourself that each block when executed is referencing a different object even though the variable name is the same and even though one would think based on the traditional sequential programming model that each bills object would have long been gone or referencing only the last object created.