How to add particle effects to an iOS App that is not a game using iOS 7 SpriteKit Particle?

Question

I need to add a rain particle effect to my app, I have been having a tough time finding ways to actually execute this idea.

I tried following this CALayer approach

Answer 1

Putting this here for visibility reasons.

The answers regarding the user of a .clear backgroundColor are correct, except that you must also set the allowsTransparency property on SKView to 'true'.

skView.allowsTransparency = true
skView.backgroundColor = .clear  // (not nil)
scene.backgroundColor = .clear

If you don't set allowsTransparency to true, and you layout your SKView over, say, a UIImageView, the composition engine will have a fit, and will send your GPU red-lining, even if only a single particle is drawn. (In the Simulator, the CPU will spike instead.)