SpriteKit collision not being detected - swift

Question

I have two nodes, one "cat" and one "rat", but for some reason I can't get their collision to be detected. I'm using this method for masks:
enum CollisionTypes: UInt32 {
case holder = 1
case chef = 2
case powerups = 4
case ingredients = 8
case utensils = 16
case floor = 32
case bag = 64
case table = 128
case tip = 256
case rat = 512
case cat = 1024
}
Here is where I initialize their physics bodies:
// Cat physics body, the node's name is "cat"
public func initializeAt(position: CGPoint) {
sprite.position = position
sprite.zPosition = 5
sprite.name = "cat"
sprite.alpha = 0.7
scene.sceneContent.addChild(sprite)
sprite.physicsBody = SKPhysicsBody(rectangleOf: sprite.size)
sprite.physicsBody!.isDynamic = false
sprite.physicsBody!.categoryBitMask = CollisionTypes.cat.rawValue
sprite.physicsBody!.contactTestBitMask = CollisionTypes.rat.rawValue
sprite.physicsBody!.collisionBitMask = CollisionTypes.rat.rawValue
// Rat physics body, the nodes name is "rat"
init() {
node.name = "rat"
node.zPosition = 5
node.physicsBody = SKPhysicsBody(rectangleOf: node.size)
node.physicsBody!.isDynamic = false
node.physicsBody!.categoryBitMask = CollisionTypes.rat.rawValue
node.physicsBody!.contactTestBitMask = CollisionTypes.cat.rawValue
node.physicsBody!.collisionBitMask = CollisionTypes.cat.rawValue
setupFrames()
}
Here is my didBegin() method. However, neither of the if statements get executed and I don't know why because I am using this method for a number of other things in my project.
func didBegin(_ contact: SKPhysicsContact) {
if let node1 = contact.bodyA.node as? SKSpriteNode,
let node2 = contact.bodyB.node as? SKSpriteNode {
if node1.name == "rat" && node2.name == "cat" {
for rat in rats {
if node1 == rat.node {
rat.die()
}
}
Cat.shared.resetPosition()
return
}
else if node1.name == "cat" && node2.name == "rat" {
for rat in rats {
if node2 == rat.node {
rat.die()
}
}
Cat.shared.resetPosition()
return
}
If I try playing around with the contactTestBitMasks and making them something different like "ingredients", then I can see that the cat and rat are interacting with ingredients but it seems like they just wont interact with eachother.

Answer 1

rats and cats won't trigger contacts with each other because both have isDynamic set to false. At least one of them needs to be dynamic before a contact is triggered.
From https://developer.apple.com/documentation/spritekit/skphysicsbody
The isDynamic property controls whether a volume-based body is
affected by gravity, friction, collisions with other objects, and forces or impulses you directly apply to the object.