animatable custom uiview

class MessageCheckMark < UIView
  attr_accessor :selected, :padding

  def initWithFrame(frame)
    if super
      self.backgroundColor = UIColor.clearColor
      self.padding = 8
    end
    self
  end

  def drawRect(rect)
    super
    unless @circle_layer
      @circle_layer = CAShapeLayer.layer
      @circle_layer.path = oval_path.CGPath
      @circle_layer.fillColor = UIColor.clearColor.CGColor
      @circle_layer.strokeColor = "#888".uicolor.CGColor
      @circle_layer.lineWidth = 1
      self.layer.addSublayer @circle_layer
    end
  end

  def oval_path(padding = nil)
    padding ||= @padding
    UIBezierPath.bezierPathWithOvalInRect CGRectMake(padding, padding, frame.size.width - padding*2, frame.size.height - padding*2)
  end

  def selected=(v)
    return if @selected == v || !@circle_layer
    CATransaction.begin
    animation = CABasicAnimation.animationWithKeyPath "path"
    animation.duration = 0.25
    animation.removedOnCompletion = false
    animation.fromValue = @circle_layer.path
    animation.toValue = oval_path(v ? 5 : padding).CGPath
    @circle_layer.path = animation.toValue
    @circle_layer.addAnimation animation, forKey: "animateCircle"
    CATransaction.commit
  end
end