title: How to draw a line in Swift 3
body: <p>I would like the user to touch 2 points and then a line is drawn between those two points. Here is what I have so far:</p>
  
  <pre><code>func drawline(){
      let context = UIGraphicsGetCurrentContext()
      context!.beginPath()
      context?.move(to: pointA)
      context?.addLine(to: pointB)
      context!.strokePath()
  }
  </code></pre>
  
  <p><code>pointA</code> is the first point the user touched and <code>pointB</code> is the second point. I get the error: </p>
  
  <pre><code>thread 1:EXC_BREAKPOINT
  </code></pre>
  
  <p>Thanks in advance for your help.</p>