Multiple physics bodies in SpriteKit - sprite-kit

Question

I have a 40x40 rectangle node, and I want to detect when the bottom touches a platform.
I tried this
let feet = SKPhysicsBody(rectangleOfSize: CGSize(width: hero.frame.size.width, height: 1), center: CGPoint(x: 0, y: -(hero.frame.size.height/2 - 0.5)))
then set the categoryBitMask, collisionBitMask, contactTestBitMaskand added it to the hero
hero.physicsBody = SKPhysicsBody(bodies: [feet])
But in didBeginContact the println() doesn't print.
I need a body for the bottom of the rectangle and one for the top, because if hero hits a platform from below the collision should push him down.
Update
Here is how I set the bit masks
let heroFeetCategory: UInt32 = 1 << 0
let edgeCategory: UInt32 = 1 << 1
let groundCategory: UInt32 = 1 << 2
let feet = SKPhysicsBody(rectangleOfSize: CGSize(width: hero.frame.size.width, height: 10), center: CGPoint(x: 0, y: -(hero.frame.size.height/2 - 5)))
feet.collisionBitMask = edgeCategory | groundCategory
feet.contactTestBitMask = groundCategory
feet.categoryBitMask = heroFeetCategory
hero.physicsBody = SKPhysicsBody(bodies: [feet])
hero.physicsBody?.usesPreciseCollisionDetection = true
hero.physicsBody?.velocity = CGVectorMake(0, 0)
hero.physicsBody?.restitution = 0.0
hero.physicsBody?.friction = 0.0
hero.physicsBody?.angularDamping = 0.0
hero.physicsBody?.linearDamping = 1.0
hero.physicsBody?.allowsRotation = false
hero.physicsBody?.mass = 0.0641777738928795
world.addChild(hero)
and for the ground
let ground = SKSpriteNode(color: UIColor.whiteColor(), size: CGSizeMake(38, 38))
ground.name = "groundName"
ground.position = CGPoint(x: 0, y: -(self.frame.size.height/2 - ground.frame.size.height/2))
ground.physicsBody = SKPhysicsBody(rectangleOfSize: ground.size)
ground.physicsBody?.collisionBitMask = edgeCategory | heroFeetCategory
ground.physicsBody?.contactTestBitMask = heroFeetCategory
ground.physicsBody?.categoryBitMask = groundCategory
world.addChild(ground)
And how I detect if they touch
func didBeginContact(contact: SKPhysicsContact) {
var notTheHero: SKPhysicsBody!;
if (contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask) {
notTheHero = contact.bodyB;
} else {
notTheHero = contact.bodyA;
}
println(notTheHero.node) // print "heroName"
if (notTheHero.categoryBitMask == groundCategory) {
println("touch began?"); // is never called
}
}

Answer 1

collision is fine, but when you print the node's name through the physics body with notTheHero.node you only access the SKNode, and not the NSString property of its name. Instead, try something like println(notTheHero.node.name);