//create the circle and center it
let circle = Circle(center: self.canvas.center, radius: 150)
circle.lineWidth = 10.0
circle.fillColor = Color(UIColor.clearColor())

//create a dash pattern
var dashPattern = [Double]()
let circumference = M_PI * circle.width
for i in 1..<Int(circumference) {
    dashPattern.append(Double(i))
}

circle.lineDashPattern = dashPattern
//add the line to the canvas
self.canvas.add(circle)
//animate it after a short wait
let a = ViewAnimation(duration:180) {
    circle.strokeColor = C4Pink
    //set the final dash phase to the entire width of the pattern
    circle.lineDashPhase = dashPattern.reduce(0, combine: +)
}

a.autoreverses = true
a.animate()