Collision Bit Mask Hero passes right through EVERY thing, even the Ground

Question

I am trying to avoid collisions between Hero and Coins, but not between Hero and Grass Ground. As soon as I apply a Collision Bit Mask to Hero, my Hero passes right through EVERY thing. I want it to pass through the Coins but not through the Grass Ground. Here is the code, any ideas?

let HEROCATEGORY: UInt32 = 0x1 << 1;
let GROUNDCATEGORY: UInt32 = 0x1 << 2;
let FIRECATEGORY: UInt32 = 0x1 << 3;
let COINCATEGORY: UInt32 = 0x1 << 4;
let NUMBERCATEGORY: UInt32 = 0x1 << 5;

heroSprite.physicsBody!.categoryBitMask = HEROCATEGORY;
heroSprite.physicsBody!.collisionBitMask = 0x10000000;
heroSprite.physicsBody!.contactTestBitMask = GROUNDCATEGORY | FIRECATEGORY | COINCATEGORY | NUMBERCATEGORY;

grassGround.physicsBody!.categoryBitMask = GROUNDCATEGORY;
grassGround.physicsBody!.collisionBitMask = 0x01000000;

coinSprite.physicsBody!.categoryBitMask = COINCATEGORY;
coinSprite.physicsBody!.contactTestBitMask = HEROCATEGORY;
coinSprite.physicsBody!.collisionBitMask = 0x10000000;

Answer 1

If hero has to detect collision with only the ground, then hero's collission bit mask should be

heroSprite.physicsBody?.collisionBitMask = GROUNDCATEGORY

To detect collision with ground and something else, you should use the OR | operator to combine both categoryBitMasks

 heroSprite.physicsBody?.collisionBitMask = GROUNDCATEGORY | SOMETHINGCATEGORY

The contactTestBitMask is used to get a callback on contact between the two bodies. We get a callback when both objects share the same space. It doesn't handle collisions.

I think what you need is contact detection with fire and coins and collision detection with ground. So just set collision bit mask of heroSprite to GROUNDCATEGORY like in my first code snippet.

let HEROCATEGORY: UInt32 = 0x1 << 1
let GROUNDCATEGORY: UInt32 = 0x1 << 2
let FIRECATEGORY: UInt32 = 0x1 << 3
let COINCATEGORY: UInt32 = 0x1 << 4
let NUMBERCATEGORY: UInt32 = 0x1 << 5

heroSprite.physicsBody!.categoryBitMask = HEROCATEGORY
heroSprite.physicsBody!.collisionBitMask = GROUNDCATEGORY // changed
heroSprite.physicsBody!.contactTestBitMask = GROUNDCATEGORY | FIRECATEGORY | COINCATEGORY | NUMBERCATEGORY

grassGround.physicsBody!.categoryBitMask = GROUNDCATEGORY
grassGround.physicsBody!.collisionBitMask = HEROCATEGORY

coinSprite.physicsBody!.categoryBitMask = COINCATEGORY
coinSprite.physicsBody!.contactTestBitMask = HEROCATEGORY