Spritekit Collision Detection not functioning properly

Question

I am using SpriteKit to build a game and have run into some trouble with collision detection. I have 2 subclasses of SKSpriteNode, Player and Enemy. They should both detect collisions with each other. Here's how I am initializing the Player object's physicsBody:

self.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:self.size];
self.physicsBody.affectedByGravity = NO;
self.physicsBody.dynamic = NO;
self.physicsBody.usesPreciseCollisionDetection = YES;
self.physicsBody.categoryBitMask = playerCategory;
self.physicsBody.collisionBitMask = enemyCategory;
self.physicsBody.contactTestBitMask = enemyCategory;

And here's how I am initializing the Enemy objects's physicsBody:

self.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:self.size];
self.physicsBody.affectedByGravity = NO;
self.physicsBody.dynamic = NO;
self.physicsBody.usesPreciseCollisionDetection = NO;
self.physicsBody.categoryBitMask = enemyCategory;
self.physicsBody.collisionBitMask = playerCategory;
self.physicsBody.contactTestBitMask = playerCategory;

I have my GameScene implementing the SKPhysicsContactDelegate protocol and I have this in its init:

self.physicsWorld.gravity = CGVectorMake(0.0, 0.0);
self.physicsWorld.contactDelegate = self;

And yet, the didBeginContact method isn't being called as it should be. I tried initializing the physicsBodies after the objects are created in the scene and still nothing. What am I doing wrong?

UPDATE 1

Here's the code that makes the bitMasks, it's in a Common.h file that is imported in Prefix.pch file.

static const uint32_t enemyCategory = 0x1 <<0;
static const uint32_t playerCategory = 0x1 <<1;

Answer 1

You need to set physicsBody.dynamic to YES for your nodes.

From the SKPhysicsBody class reference:

dynamic

A Boolean value that indicates whether the physics body is moved by the physics simulation.

The default value is YES. If the value is NO, then the physics body ignores all forces and impulses applied to it.