Get angle from 2 positions

Question

I have 2 objects and when I move one, I want to get the angle from the other.

For example:

Object1X = 211.000000, Object1Y = 429.000000
Object2X = 24         


        

Answer 1

Here's how I'm doing it in Swift for those interested, it's based on @bshirley's answer above w/ a few modifications to help match to the calayer rotation system:

extension CGFloat {
    var degrees: CGFloat {
        return self * CGFloat(180) / .pi
    }
}

extension CGPoint {
    func angle(to comparisonPoint: CGPoint) -> CGFloat {
        let originX = comparisonPoint.x - x
        let originY = comparisonPoint.y - y
        let bearingRadians = atan2f(Float(originY), Float(originX))
        var bearingDegrees = CGFloat(bearingRadians).degrees

        while bearingDegrees < 0 {
            bearingDegrees += 360
        }

        return bearingDegrees
    }
}

This provides a coordinate system like this:

        90
180              0
        270

Usage:

point.angle(to: point2)
CGPoint.zero.angle(to: CGPoint(x: 0, y: 1)) // 90