title: How do can I make things collide and do things when they do?
body: <p>I have been trying to do this for ages, what I would like to do is, I have a rocket and missiles coming down in my Scene and I want a very very simple explanation on how to do this so when the missiles collide with the rocket it will run a function in your code just call the function "func" and 
  I am not very familiar with SKPhysicsBody and enums so please explain those as well please (This is in swift spriteKit).
  Thanks in Advance.</p>