Updating UIView makes a hash of subview's alignment / Swift - ios

Question

I'm new in Swift. I want to make an app with a moving subview. I'm testing the app, and when i touch down the button, the subview moves with the correct value, but when the parent UIView updates because of changing label, the subview jump back to the origin coordinate what i set up in the storyboard. I use core graphics to draw circle. I want to move the circle on the screen by tap a button. How can i solved this problem?
class ViewController: UIViewController {
#IBOutlet weak var movingItem: MovingItem! /* inheritance from UIView */
#IBAction func move() {
self.movingItem.frame = CGRect(x: movingItem.frame.origin.x + 5.0,
y: movingItem.frame.origin.y,
width: movingItem.frame.width,
height: movingItem.frame.height)
}
override func viewDidLoad() {
self.movingItem.frame = CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0)
self.movingItem.setNeedsDisplay()
}
//more code...
}
#IBDesignable
class MovingItem: UIView {
override func drawRect(rect: CGRect) {
var context = UIGraphicsGetCurrentContext()
CGContextBeginPath(context)
var rectForCircle = CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0)
CGContextAddEllipseInRect(context, rectForCircle)
UIColor.redColor().setFill()
CGContextDrawPath(context, kCGPathFill)
}
}

Answer 1

Try instead of
var rectForCircle = CGRect(x: 0.0, y: 0.0, width: 50.0, height: 50.0)
CGContextAddEllipseInRect(context, rectForCircle)
like this:
CGContextAddEllipseInRect(context, self.frame)
and insert line
self.movingItem.setNeedsDisplay()
after
self.movingItem.frame = CGRect(x: movingItem.frame.origin.x + 5.0,
y: movingItem.frame.origin.y,
width: movingItem.frame.width,
height: movingItem.frame.height)