Differentiating Between Different Bitmasks - swift3

Question

I am having trouble figuring out how to differentiate between different bitmasks.
I want this to happen:
/*func didBegin(_ contact: SKPhysicsContact) {
if (spaceship1 collides with spaceship2) {
print("contact between 1 and 2")
}
if (spaceship1 collides with spaceship3) {
print("contact between 1 and 3")
}
}
*/
Here's the code I have tried:
func didBegin(_ contact: SKPhysicsContact) {
if (contact.bodyA.categoryBitMask = enemyCategory && contact.bodyB.categoryBitMask = enemy2Category) {
print("contact between 1 and 2")
}
}
Could I get some help?
EDIT: Here's the other code:
import SpriteKit
import GameplayKit
class GameScene: SKScene, SKPhysicsContactDelegate {
let enemy2Category: UInt32 = 1
let enemyCategory: UInt32 = 2
let enemy3Category: UInt32 = 3
var spaceship1: SKSpriteNode!
var spaceship2: SKSpriteNode!
var spaceship3: SKSpriteNode!
override func didMove(to view: SKView) {
self.physicsWorld.contactDelegate = self
spaceship1 = SKSpriteNode(imageNamed: "Spaceship");
spaceship1.setScale(CGFloat(0.1))
spaceship1.position = CGPoint(x: self.frame.width / 2, y: (self.frame.height / 2));
spaceship1.name = "spaceship1";
spaceship1.physicsBody = SKPhysicsBody(circleOfRadius: spaceship1.size.width / 2);
spaceship1.physicsBody?.isDynamic = true // apply gravity, friction, and collision
spaceship1.physicsBody?.affectedByGravity = true;
spaceship1.physicsBody?.allowsRotation = false
spaceship1.physicsBody = SKPhysicsBody(circleOfRadius: spaceship1.size.width / 2);
spaceship1.physicsBody?.categoryBitMask = enemy2Category
spaceship1.physicsBody?.collisionBitMask = enemyCategory
spaceship1.physicsBody?.contactTestBitMask = enemyCategory
spaceship2 = SKSpriteNode(imageNamed: "Spaceship");
spaceship2.setScale(CGFloat(0.1))
spaceship2.position = CGPoint(x: self.frame.width / 2, y: (spaceship1.position.y + 300));
spaceship2.name = "spaceship2";
spaceship2.physicsBody = SKPhysicsBody(circleOfRadius: spaceship2.size.width / 2);
spaceship2.physicsBody?.isDynamic = true // apply gravity, friction, and collision
spaceship2.physicsBody?.affectedByGravity = false;
spaceship2.physicsBody?.allowsRotation = false
spaceship2.physicsBody = SKPhysicsBody(circleOfRadius: spaceship2.size.width / 2);
spaceship2.physicsBody?.categoryBitMask = enemyCategory
spaceship2.physicsBody?.collisionBitMask = enemy2Category
spaceship2.physicsBody?.contactTestBitMask = enemy2Category
spaceship3 = SKSpriteNode(imageNamed: "Spaceship");
spaceship3.setScale(CGFloat(0.1))
spaceship3.position = CGPoint(x: self.frame.width / 2, y: (spaceship1.position.y + 300));
spaceship3.name = "spaceship3";
spaceship3.physicsBody = SKPhysicsBody(circleOfRadius: spaceship2.size.width / 2);
spaceship3.physicsBody?.isDynamic = true // apply gravity, friction, and collision
spaceship3.physicsBody?.affectedByGravity = false;
spaceship3.physicsBody?.allowsRotation = false
spaceship3.physicsBody = SKPhysicsBody(circleOfRadius: spaceship2.size.width / 2);
spaceship3.physicsBody?.categoryBitMask = enemy3Category
spaceship3.physicsBody?.collisionBitMask = enemy2Category | enemyCategory
spaceship3.physicsBody?.contactTestBitMask = enemy2Category | enemyCategory
addChild(spaceship1)
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
addChild(spaceship3)
}
override func update(_ currentTime: TimeInterval) {
spaceship1.physicsBody?.affectedByGravity = false;
}
}
I'm just trying to figure out how to detect which bitmasks come into contact with each other. Like if spaceship1 comes into contact with spaceship2, it prints yay, but if spaceship1 comes into contact with spaceship 3, it prints "wow"

Answer 1

There is a documentation article that tries to explain bit masks as used in Sprite-Kit collision and contacts, but I can no longer link to it. Try to find the 'Documentation' page, tag 'Sprite-Kit' then the 'Manipulating contactTest and collison bitmasks to enable/disable specific contact and collisions.' article under 'SKNode Collision'.
One obvious problem is this line :
let enemy3Category: UInt32 = 3
All bitmasks have to be thought of in binary, and in binary 3 is 11. This is the '1' bit and the '2' bit both being set to 1. Category definitions should only have 1 bit set to 1 which you ensure by using exact powers of 2 for your categories - 1, 2, 4, 8, 16, 32, etc.
Objects in your scene that need to collide/contact should belong to only one category initially. For more advanced contacts and collisions, a sprite can belong to multiple categories.

Answer 2

You are missing an = in your if statement.
func didBegin(_ contact: SKPhysicsContact) {
if (contact.bodyA.categoryBitMask == enemyCategory && contact.bodyB.categoryBitMask == enemy2Category) {
print("contact between 1 and 2")
}
}

Answer 3

This sets firstBody to the smaller bitmask And sets secondBody to the larger one
var firstBody = SKPhysicsBody()
var secondBody = SKPhysicsBody()
if contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask {
firstBody = contact.bodyA
secondBody = contact.bodyB
}else{
firstBody = contact.bodyB
secondBody = contact.bodyA
}
Assuiming bitmask1 is smaller than 2 and 3.
if firstBody.categoryBitMask == bitMask1 && secondBody.categoryBitMask == bitMask.bitmask3 {
print("a")
//If ball hits a pad, activate the pad
}else if firstBody.categoryBitMask == bitMask1 && secondBody.categoryBitMask == bitMask.bitmask2 {
print("e")
}