在Swift 3中将参数传递给UIView子类

Question

I'm trying to pass argument to a UIView subclass. My code seems to work but after initialization the all the argument become nil: when lineWidth (one of the argument) is called in the draw function I've this error:

"fatal error: unexpectedly found nil while unwrapping an Optional value"

This is my code for the viewController:

import UIKit

class ViewController: UIViewController,UIGestureRecognizerDelegate,UIScrollViewDelegate {
    @IBOutlet weak var scrollView: UIScrollView!
    @IBOutlet weak var matrixView = UIMatrixView(mat: [[Bool]](),gRows:20,gCols:20,lWidth:2)

    override func viewDidLoad() {
        super.viewDidLoad()
        // scrollView.delegate = self
    }

    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return self.matrixView
    }
}

And this is for the UIView subclass:

import UIKit

class UIMatrixView: UIView {
    var matrix : [[Bool]]!
    var gridRows : Int!
    var gridCols : Int!
    var lineWidth : Int!

    init(mat: [[Bool]], gRows : Int, gCols : Int, lWidth : Int){
        print("here")
        self.matrix=mat
        self.gridRows=gRows
        self.gridCols=gCols
        self.lineWidth=lWidth
        super.init(frame: CGRect())
        print(lineWidth)
    }

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)!
    }

    // Only override draw() if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func draw(_ rect: CGRect) {
        print(lineWidth)
    }
}

Answer 1

The custom UIView marked as a weak property.

Strong Reference on it is not keep after creation in the code.

Property which is marked with IBOutlet can be set in Storyboard.

Or otherwise, set weak reference after addition as subview ( addSubview ) :

func appendMatrixView() {
  let mView = MatrixView(...
 //Important lines.....
   addSubview(mView)
   self.matrixView = mView; 
}