Nicholas Muir Nicholas Muir - 3 months ago 14
iOS Question

Circle Layer error with super.init - Swift

This is going to be a really basic question.

I am working through this answer:
Animate drawing of a circle

But no matter how I format it I get an error. I can see from the error that I have not initialized circle and I am sure it is just a positioning thing but not sure what or how to do that correctly or what is wrong with how I have layout.

When I try like this i get the error ('self.circleLayer' not initialized at super.init call):

import UIKit

class CircleView: UIView {

let circleLayer: CAShapeLayer!

override init(frame: CGRect) {
super.init(frame: frame)


self.backgroundColor = UIColor.clearColor()

// Use UIBezierPath as an easy way to create the CGPath for the layer.
// The path should be the entire circle.
let circlePath = UIBezierPath(arcCenter: CGPoint(x: frame.size.width / 2.0, y: frame.size.height / 2.0), radius: (frame.size.width - 10)/2, startAngle: 0.0, endAngle: CGFloat(M_PI * 2.0), clockwise: true)

// Setup the CAShapeLayer with the path, colors, and line width
circleLayer = CAShapeLayer()
circleLayer.path = circlePath.CGPath
circleLayer.fillColor = UIColor.clearColor().CGColor
circleLayer.strokeColor = UIColor.redColor().CGColor
circleLayer.lineWidth = 5.0;

// Don't draw the circle initially
circleLayer.strokeEnd = 0.0

// Add the circleLayer to the view's layer's sublayers
layer.addSublayer(circleLayer)
}


required init(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}

}


Then tried moving it to after the initializer like this which doesn't give me an error):

import UIKit

class CircleView: UIView {

override init(frame: CGRect) {
super.init(frame: frame)

let circleLayer: CAShapeLayer!
self.backgroundColor = UIColor.clearColor()

// Use UIBezierPath as an easy way to create the CGPath for the layer.
// The path should be the entire circle.
let circlePath = UIBezierPath(arcCenter: CGPoint(x: frame.size.width / 2.0, y: frame.size.height / 2.0), radius: (frame.size.width - 10)/2, startAngle: 0.0, endAngle: CGFloat(M_PI * 2.0), clockwise: true)

// Setup the CAShapeLayer with the path, colors, and line width
circleLayer = CAShapeLayer()
circleLayer.path = circlePath.CGPath
circleLayer.fillColor = UIColor.clearColor().CGColor
circleLayer.strokeColor = UIColor.redColor().CGColor
circleLayer.lineWidth = 5.0;

// Don't draw the circle initially
circleLayer.strokeEnd = 0.0

// Add the circleLayer to the view's layer's sublayers
layer.addSublayer(circleLayer)
}


required init(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}

}


But then when I try to put a function in my viewcontroller.swift that references circleLayer I get unresolved identifier:

func animateCircle(duration: NSTimeInterval) {
// We want to animate the strokeEnd property of the circleLayer
let animation = CABasicAnimation(keyPath: "strokeEnd")

// Set the animation duration appropriately
animation.duration = duration

// Animate from 0 (no circle) to 1 (full circle)
animation.fromValue = 0
animation.toValue = 1

// Do a linear animation (i.e. the speed of the animation stays the same)
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)

// Set the circleLayer's strokeEnd property to 1.0 now so that it's the
// right value when the animation ends.
circleLayer.strokeEnd = 1.0

// Do the actual animation
circleLayer.addAnimation(animation, forKey: "animateCircle")
}


I am sure it just something really simple but I am not sure what.

Thanks for your help.

Answer

From the documentation

Safety check 1

A designated initializer must ensure that all of the properties introduced by its class are initialized before it delegates up to a superclass initializer.

Initialize circleLayer in the declaration line and move self.backgroundColor = ... after super.init

class CircleView: UIView {

  let circleLayer = CAShapeLayer()

  override init(frame: CGRect) {

    // Use UIBezierPath as an easy way to create the CGPath for the layer.
    // The path should be the entire circle.
    let circlePath = UIBezierPath(arcCenter: CGPoint(x: frame.size.width / 2.0, y: frame.size.height / 2.0), radius: (frame.size.width - 10)/2, startAngle: 0.0, endAngle: CGFloat(M_PI * 2.0), clockwise: true)

    super.init(frame: frame)
    // Setup the CAShapeLayer with the path, colors, and line width

    self.backgroundColor = UIColor.clearColor()
    circleLayer.path = circlePath.CGPath
    circleLayer.fillColor = UIColor.clearColor().CGColor
    circleLayer.strokeColor = UIColor.redColor().CGColor
    circleLayer.lineWidth = 5.0;

    // Don't draw the circle initially
    circleLayer.strokeEnd = 0.0

    // Add the circleLayer to the view's layer's sublayers
    layer.addSublayer(circleLayer)
  }


  required init(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }

}
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