Collision Detection Not Working in SpriteKit - objective-c

Question

I am stuck on this for several hours now which seems like a very simple task. I have an SKSpriteNode call Ball which is declared below:
-(instancetype) initWithType:(BallType) ballType
{
if(ballType == UserBall) {
self = [super initWithImageNamed:USER_BALL_IMAGE];
self.physicsBody.categoryBitMask = BBPhysicsCategoryUserBall;
self.physicsBody.contactTestBitMask = BBPhysicsCategoryRedBall | BBPhysicsCategoryWorld;
self.physicsBody.collisionBitMask = 0;
}
// setup physical aspects of the ball
self.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:self.size.width/2];
self.physicsBody.friction = 0.0f;
self.physicsBody.dynamic = YES;
return self;
}
I create another SKSpriteNote "redBall" as below:
SKSpriteNode *redBall = [[SKSpriteNode alloc] initWithImageNamed:RED_BALL_IMAGE];
redBall.physicsBody.categoryBitMask = BBPhysicsCategoryRedBall;
redBall.physicsBody.contactTestBitMask = BBPhysicsCategoryUserBall;
redBall.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:redBall.size.width/2];
redBall.physicsBody.friction = 0.0f;
redBall.position = CGPointMake(self.size.width/2 , self.size.height/4);
[self addChild:redBall];
[redBall.physicsBody applyImpulse:CGVectorMake(0.0, 0.5)];
My GameScene inherits from SKScene and implements the SKPhysicsContactDelegate protocol. I assign the contactDelegate as follows:
-(void) setupPhysicsWorld {
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.physicsWorld.gravity = CGVectorMake(0.0f, 0.0f);
self.physicsBody.friction = 0.0f;
self.physicsBody.categoryBitMask = BBPhysicsCategoryWorld;
self.physicsWorld.contactDelegate = self;
}
But for some reason the didBeginContact is NEVER CALLED!!! I am going crazy as why it is not being called?

Answer 1

-(instancetype) initWithType:(BallType) ballType
{
if(ballType == UserBall) {
self = [super initWithImageNamed:USER_BALL_IMAGE];
self.physicsBody.categoryBitMask = BBPhysicsCategoryUserBall;
self.physicsBody.contactTestBitMask = BBPhysicsCategoryWorld;
self.physicsBody.collisionBitMask = 0;
}
// setup physical aspects of the ball
self.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:self.size.width/2];
self.physicsBody.friction = 0.0f;
self.physicsBody.dynamic = YES;
return self;
}
SKSpriteNode *redBall = [[SKSpriteNode alloc] initWithImageNamed:RED_BALL_IMAGE];
redBall.physicsBody.categoryBitMask = BBPhysicsCategoryRedBall;
redBall.physicsBody.contactTestBitMask = BBPhysicsCategoryUserBall;
redBall.physicsBody = [SKPhysicsBody bodyWithCircleOfRadius:redBall.size.width/2];
redBall.physicsBody.friction = 0.0f;
redBall.position = CGPointMake(self.size.width/2 , self.size.height/4);
[self addChild:redBall];
[redBall.physicsBody applyImpulse:CGVectorMake(0.0, 0.5)];
you are setting redBall.physicsBody.contactTestBitMask twice