Objects falling towards earth regardless of device orientation

Question

I have seen two ways to describe falling objects behaviour for different device orientation using CoreMotion framework. I have tried both version in code and they both seem to behave as what I expect, i.e. falling toward earth regardless of device orientation.

I'm just curious why both version behave the same, even though for the first version, the acceleration in x and y direction, i.e. dx and dy, are switched at landscape orientation?

1)

if var dx = data?.acceleration.x, var dy = data?.acceleration.y {
                            switch UIDevice.currentDevice().orientation {
                            case .Portrait:
                                dy = -dy
                            case .PortraitUpsideDown:
                                break
                            case .LandscapeRight:
                                swap(&dx, &dy)
                            case .LandscapeLeft:
                                swap(&dx, &dy)
                                dy = -dy 
                            default:
                                dx = 0
                                dy = 0
                            }
                            gravity.gravityDirection = CGVector(dx: dx, dy: dy)
                        }

2)

if var dx = data?.acceleration.x, var dy = data?.acceleration.y {
                                switch UIDevice.currentDevice().orientation {
                                case .Portrait:
                                    dy = -dy
                                case .PortraitUpsideDown:
                                    break
                                case .LandscapeRight:
                                    break
                                case .LandscapeLeft:
                                    break
                                default:
                                    dx = 0
                                    dy = 0
                                }
                                gravity.gravityDirection = CGVector(dx: dx, dy: dy)
                            }

Answer 1

I guess you are using the simulator, so gravity is always orthogonal to the bottom.

The behaviour should differ on a real device imo., as you will always tilt the device at least slightly.