Written by Paul Hudson @twostraws
Enabling physics in SpriteKit is just one line of code, but sometimes you want your physics to be a little more nuanced. For example, your player might have circle physics and should respond to gravity, whereas walls might have rectangle physics and not respond to gravity – they are there to be bounced off, but nothing more.
This problem is solved in SpriteKit by using the isDynamic property. It's true by default, which means that your objects respond to the world's environment as you would expect, but if you set it to be false then you get an object that has active physics but doesn't move as a result of those physics.
Here's an example:
let wall = SKSpriteNode(imageNamed: "wall")
wall.position = CGPoint(x: 512, y: 0)
wall.physicsBody = SKPhysicsBody(circleOfRadius: wall.size.width / 2.0)
wall.physicsBody?.isDynamic = false
addChild(wall)Available from iOS 7.0 – see Hacking with Swift tutorial 11
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