swift – 如何用CALayer创建一个圈子？

我有下面的代码测试,但是当我给它的约束,它变成一个小圆圈：

override func drawRect(rect: CGRect) {
var path = UIBezierPath(ovalInRect: rect)
fillColor.setFill()
path.fill()

//set up the width and height variables
//for the horizontal stroke
let plusHeight:CGFloat = 300.0
let plusWidth:CGFloat = 450.0

//create the path
var plusPath = UIBezierPath()

//set the path's line width to the height of the stroke
plusPath.linewidth = plusHeight

//move the initial point of the path
//to the start of the horizontal stroke
plusPath.movetoPoint(CGPoint(
  x:self.bounds.width/2 - plusWidth/2 + 0.5,y:self.bounds.height/2 + 0.5))

//add a point to the path at the end of the stroke
plusPath.addLinetoPoint(CGPoint(
  x:self.bounds.width/2 + plusWidth/2 + 0.5,y:self.bounds.height/2 + 0.5))

}

根据需要更改半径和fillColor.