Example of subclassing AngleGradientLayer to allow borders.

AngleGradientBorderTutorial_02.swift

//
//  AngleGradientBorderLayer.swift
//  AngleGradientBorderTutorial
//

import UIKit

class AngleGradientBorderLayer: AngleGradientLayer {

  // Properties
  var gradientBorderWidth: CGFloat = 1

  // Override to add a border shape to AngleGradientLayer.
  override func drawInContext(ctx: CGContext!) {
    // Draw a shape that fills the view minus the width of your final border.
    // This can be any shape you want to make a border out of.
    // This example draws a circle.
    let shapePath = UIBezierPath(roundedRect: CGRectInset(bounds, gradientBorderWidth, gradientBorderWidth), cornerRadius: bounds.height / 2)

    // Copy the path of the shape and turn it into a stroke.
    let shapeCopyPath = CGPathCreateCopyByStrokingPath(shapePath.CGPath, nil, gradientBorderWidth, kCGLineCapButt, kCGLineJoinBevel, 0)

    CGContextSaveGState(ctx)

    // Add the stroked path to the context and clip to it.
    CGContextAddPath(ctx, shapeCopyPath)
    CGContextClip(ctx)

    // Call our super class's (AngleGradientLayer) #drawInContext
    // which will do the work to create the gradient.
    super.drawInContext(ctx)

    CGContextRestoreGState(ctx)
  }
}