Swift drawInRect Can't unwrap Optional.None

Question

I am trying to translate an old code of mine from objective-c to swift.

But I get the following error on self.image.drawInRect():

fatal error: Can't unwrap Optional.None

I have this class called Canvas, it is a subclass of UIImageView and its set on storyboard and its initialized on my only ViewController :

init(coder aDecoder: NSCoder!) {
    pref = NSUserDefaults.standardUserDefaults()

    currentPlay = Play()
    canvas = Canvas(coder: aDecoder)
    super.init(coder: aDecoder)
}

This is my Canvas.Swift

import UIKit

class Canvas: UIImageView {

    var path:UIBezierPath = UIBezierPath()
    var drawColor:UIColor = UIColor.greenColor()
    var lastLocation:CGPoint = CGPoint()

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

    // handling touches

    override func touchesBegan(touches: NSSet!, withEvent event: UIEvent!) {
        let touch:UITouch  = touches.anyObject() as UITouch
        lastLocation = touch.locationInView(self.superview)
    }

    override func touchesMoved(touches: NSSet!, withEvent event: UIEvent!) {
        let touch:UITouch  = touches.anyObject() as UITouch
        let location = touch.locationInView(self.superview)

        UIGraphicsBeginImageContext(self.frame.size)
        self.image.drawInRect(self.frame)
        path = UIBezierPath()
        path.lineWidth = 8;
        path.lineCapStyle = kCGLineCapRound;
        drawColor.setStroke()

        path.moveToPoint(CGPointMake(lastLocation.x, lastLocation.y))

        path.addLineToPoint(CGPointMake(location.x, location.y))
        path.stroke()

        self.image = UIGraphicsGetImageFromCurrentImageContext();
        lastLocation = location

        path.closePath()
        UIGraphicsEndImageContext();
    }

    override func touchesEnded(touches: NSSet!, withEvent event: UIEvent!) {
        // nothing yet
    }
}

ps: if I remove the drawInRect line I can get the drawing for the moment if goes through the touchedMoved... but since the context gets reset, it does not persist on the image

Adding an image to the canvas works fine... but if the image has a different size, the canva go wild... — Andre Cytryn

JuJoDi JuJoDi · Accepted Answer · 2014-07-03T20:44:25

UIImageView is generally init'd with an image - but in your case you're unarchiving it and assuming the image property holds a valid image. Since the image property is implicitly unwrapped (it's defined as var image: UIImage!) it does not give you a compile time error, and instead crashes at runtime.

To unwrap the image and use drawInRect when the image is available replace self.image.drawInRect(self.frame) with

if let image = self.image {
    image.drawInRect(self.frame)
}

Swift drawInRect Can't unwrap Optional.None

1 Answers