import UIKit

​

class CustomView: UIView {

    override var intrinsicContentSize: CGSize {

        return CGSize(width: 100, height: 100)

    }

}

​

class ViewController: UIViewController {

    override func viewDidLoad() {

        let newView = CustomView()

        newView.backgroundColor = UIColor.red

        view.addSubview(newView)

        newView.translatesAutoresizingMaskIntoConstraints = false

        let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)

        let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)

        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint])

    }

}