Question

I have a UIViewController which has a UIView in it and I want to draw a straight dotted line on it. What is the easiest and performant way to do this? How do I do this? It will just be a straight horizontal dotted line of width 150 with gray color. I’ve looked around and it seems that using
CGContextSetLineDash is the solution and here’s what I have so far:

-(void) drawRect:(CGRect) rect
{
  CGContextRef context = UIGraphicsGetCurrentContext();
  CGContextSetLineWidth(context, 100);
  CGFloat dashes[] = {1,1};
  CGContextSetLineDash(context, 2.0, dashes, 2);
  CGContextStrokePath(context);
}

Answer 1

CGContextStrokePath draws the current path, however, you never add any path to your context, so nothing is drawn.

Add the following two lines before your CGContextStrokePath call and you should see something:

CGContextMoveToPoint(context, 0, self.bounds.size.height * 0.5);
CGContextAddLineToPoint(context, self.bounds.size.width, self.bounds.size.height * 0.5);

If you haven’t already set your stroke color, you should also add something like this (50% gray):

CGContextSetRGBStrokeColor(context, 0.5, 0.5, 0.5, 1.0);

I’m not sure if the result is really what you want, a 100 point dotted line with a pattern of {1, 1} will look more like an rectangle with a pinstripe pattern than like a dotted line. If you want your dots to be circles, you will have to draw those manually in some sort of loop.