Specific Head On Collision in Swift 4 - swift

Question

I am new to iOS development and I made an infinite runner game. As you can see in the function below, the player dies when it collides with an obstacle. However, the player dies whenever it collides with any side of the obstacle. How can I limit this collision detection to a specific side of the frame of the obstacle?
func didBegin(_ contact: SKPhysicsContact) { //so the player can't jump while in the air
var firstBody = SKPhysicsBody()
var secondBody = SKPhysicsBody()
if contact.bodyA.node?.name == "Player" {
firstBody = contact.bodyA
secondBody = contact.bodyB
} else {
firstBody = contact.bodyB
secondBody = contact.bodyA
}
if firstBody.node?.name == "Player" && secondBody.node?.name == "Ground" { //if colliding with ground
canJump = true //can jump when on ground
}
if firstBody.node?.name == "Player" && secondBody.node?.name == "Bus" || firstBody.node?.name == "Player" && secondBody.node?.name == "Obstacle" {
// kill player and prompt buttons
playerDied()
}
}

Answer 1

You may try to calculate the intersection between two colliding nodes, then just checking width and height of the resulting frame should be enough to detect the collision side, a rough explanation:
collision left/right
collision top/down
for a infinite runner game this check should be enough:
if firstBody.node?.name == "Player" && secondBody.node?.name == "Obstacle" {
let intersection = firstBody.node!.frame.intersection(secondBody.node!.frame)
if intersection.height > intersection.width { // collision left/right
playerDied()
} else { // collision top/down
//...//
}
}