swift uiview does not have a member named center

Question

This is my RectangleView:

import UIKit

class RectangleView: UIView
{
    init(frame: CGRect)
    {
        // Initialization code
        super.init(frame: frame)
    }

    /*
    override func drawRect(rect: CGRect)
    {
        // Drawing code
    }
    */
}

I add this RectangleView on my CustomViewController:

import UIKit

class CustomViewController: UIViewController
{
    var ballX:Int = 0
    var ballY:Int = 0
    let BALLWIDTH:Int = 50
    let BALLHEIGHT:Int = 50
    var navigationHeight:Double = 0.0
    var pos:CGPoint?
    var rectangleView:RectangleView?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        self.ballX = Int(arc4random_uniform(320));
        self.ballY = Int(arc4random_uniform(480));
        self.navigationHeight = Double(self.navigationController.navigationBar.frame.size.height)
        var rect = CGRect(x: 0, y: 0, width: self.BALLWIDTH, height: self.BALLHEIGHT)
        self.pos = CGPoint(x: self.ballX, y: self.ballY);

        println("x: \(self.ballX), y: \(self.ballY)")

        self.rectangleView = RectangleView(frame: rect)
        self.rectangleView!.backgroundColor = UIColor.redColor()

        self.view.addSubview(self.rectangleView!)

        NSTimer.scheduledTimerWithTimeInterval(0.05, target: self, selector: Selector("moveBall"), userInfo: nil, repeats: true)
    }

    func moveBall()
    {
        self.rectangleView!.center = CGPointMake(self.rectangleView!.center + self.pos!.x, self.rectangleView!.center + self.pos!.y)
    }
...

And I get a error message

'RectangleView?' does not have a member named 'center'

Should I define this center on my RectangleView? My RectangleView inherits from UIView, so I feel very confused. Thanks your help.

---

Edit

I use this code

func moveBall()
{
    if let rv = self.rectangleView {
        rv.center = CGPointMake(rv.center + self.pos!.x, rv.center + self.pos!.y)
    }

I get the new error message

'CGPoint' is not convertible to 'UInt8'

I think the rv.center type is UInt8, but self.post!.x is nsnumber, so I how could I convert to CGPointMake accept type? I have convert UInt8(self.pos!.x) and convert calculate result to CGPointMake accept type again?

Have any other best method? Thanks your help.

Answer 1

The values returned by !-unwrapping an optional are currently immutable (see Lattner's explanation).

Try:

if let rv = self.rectangleView {
  rv.center = ...
}

I think this can be considered a known bug in Swift.