Travis Kirton

Dash Phase

Let’s say you have a pattern like this 5,10,15,20,25,30,35,40,45,50,55,60… Which ends up being 390 points wide. And, let’s also say you have a line that is 200pt wide.

You can offset the phase (i.e. where the patten starts) so that you can see the portion that would otherwise lie outside the shape’s bounds.

shape.lineDashPhase = 200.0


//create the line and center it
let points = (Point(0,, Point(canvas.width,
let line = Line(points)
line.lineWidth = 100.0

//create a dash pattern
var dashPattern = [Double]()
for i in Int(line.lineWidth)..<Int(canvas.width + line.lineWidth) {
line.lineDashPattern = dashPattern

let a = ViewAnimation(duration:30.0) {
    line.strokeColor = C4Pink
    //set the final dash phase to the entire width of the pattern
    line.lineDashPhase = dashPattern.reduce(0, combine: +)

a.autoreverses = true
a.repeats = true

Check out the way we use reduce to calculate the sum of the entire pattern array.