func draw(_ dirtyRect: NSRect) is not called - draw

Question

I wrote this code in Swift 3.0 but draw method is not called from func drawBorder by needsDisplay = true; drawBorder is called by clicking button in another view.
Thanks for any hint.
class clsDrawView: NSView {
private var redraw = false
var border = NSBezierPath()
var color = NSColor()
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
// Drawing code here.
if redraw {
color.setStroke()
border.stroke()
}
}
func drawBorder() {
redraw = true
color = NSColor.blue
border.lineWidth = CGFloat(10)
border.move(to: NSPoint(x: 20, y: 20))
border.line(to: NSPoint(x: 50, y: 50))
needsDisplay = true
}
}

Answer 1

Try to call setNeedsDisplay(_:) method on your view, this should call draw(_:) method. Never call draw(_:) method by yourself.

Answer 2

Finally I solved it via notification
class clsDrawView: NSView {
private var draw = false
private var border = NSBezierPath()
var color = NSColor()
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
NotificationCenter.default.addObserver(self, selector: #selector(self.drawBorder(_:)), name: NSNotification.Name(rawValue: "drawBorder"), object: nil)
// Drawing code here.
if draw {
color.setStroke()
border.stroke()
}
}
func drawBorder(_ notification: NSNotification) {
draw = true
color = NSColor.black
NSBezierPath.setDefaultLineWidth(4)
border.lineWidth = CGFloat(10)
border = NSBezierPath(rect: self.bounds)
needsDisplay = true
}
}
Notification is postec from ViewController like this
#IBAction func btnDraw(_ sender: NSButton) {
NotificationCenter.default.post(name: NSNotification.Name.init(rawValue: "drawBorder"), object: sender)
}