How to set image in circle in swift

import UIKit

class ViewController: UIViewController {
  @IBOutlet weak var image: UIImageView!

  override func viewDidLoad() {
    super.viewDidLoad()
    
    image.layer.borderWidth = 1
    image.layer.masksToBounds = false
    image.layer.borderColor = UIColor.black.cgColor
    image.layer.cornerRadius = image.frame.height/2
    image.clipsToBounds = true
}

If you want it on an extension

import UIKit

extension UIImageView {
    
    func makeRounded() {
        
        layer.borderWidth = 1
        layer.masksToBounds = false
        layer.borderColor = UIColor.black.cgColor
        layer.cornerRadius = self.frame.height / 2
        clipsToBounds = true
    }
}

That is all you need....

Based in the answer of @DanielQ

Swift 4 and Swift 3

import UIKit

extension UIImageView {

    func setRounded() {
        self.layer.cornerRadius = (self.frame.width / 2) //instead of let radius = CGRectGetWidth(self.frame) / 2
        self.layer.masksToBounds = true
    }
}

You can use it in any ViewController with:

imageView.setRounded()

You can simple create extension:

import UIKit

extension UIImageView {

   func setRounded() {
      let radius = CGRectGetWidth(self.frame) / 2
      self.layer.cornerRadius = radius
      self.layer.masksToBounds = true
   }
}

and use it as below:

imageView.setRounded()