TouchesMovedで動かせるUIViewを作ろう

UIImageViewを例にすると、UIImageViewを継承したクラスを新しく作って、その中でtouchesMovedを書けばOK

.swift

class TouchImageView: UIImageView {
    override init(image: UIImage?) {
        super.init(image: image)
        self.isUserInteractionEnabled = true
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesMoved(touches, with: event)
        next?.touchesMoved(touches, with: event)
        let touch = touches.first!
        let prevPos = touch.previousLocation(in: self.superview)
        let nowPos = touch.location(in: self.superview)
        let diff = nowPos! - prevPos!
        self.layer.position += diff
    }
}

extension CGPoint: AdditiveArithmetic {
    public static func - (lhs: CGPoint, rhs: CGPoint) -> CGPoint {
        return CGPoint(x: lhs.x - rhs.x, y: lhs.y - rhs.y)
    }
    public static func + (lhs: CGPoint, rhs: CGPoint) -> CGPoint {
        return CGPoint(x: lhs.x + rhs.x, y: lhs.y + rhs.y)
    }
    func toCGSize() -> CGSize {
        return CGSize(width: self.x, height: self.y)
    }
}