I'm creating my UI programmatically and I want to make my `UITextfield` `topAnchor` to be based off the height of its containing `UIView` but it's not working.

My `UITextfield` is inside a `UIView` and I want its `topAnchor` to be 0.15 the height of the `UIView` as such - `containerView.frame.size.height * 0.15` but it seems the value is not picking up. All this is done in a `UIView` subclass and called in the `ViewController`

```
        let containerView: UIView
        containerView.translatesAutoresizingMaskIntoConstraints = false
        self.addSubview(containerView)

        NSLayoutConstraint.activate([
            containerView.centerXAnchor.constraint(equalTo: self.centerXAnchor),
            containerView.widthAnchor.constraint(equalTo: self.widthAnchor, multiplier: 0.9),
            containerView.topAnchor.constraint(equalTo: stepTitleLabel.bottomAnchor, constant: 50),
            containerView.heightAnchor.constraint(equalTo: self.heightAnchor, multiplier: 0.65)
            ])

        let userTextField: UITextField
        userTextField?.tag = 1
        userTextField?.translatesAutoresizingMaskIntoConstraints = false
        containerView.addSubview(userTextField)

        userTextField.setNeedsLayout()
        print("containerView.frame.size.height * 0.15:\(containerView.frame.size.height * 0.15)")
        NSLayoutConstraint.activate([
            (userTextField.centerXAnchor.constraint(equalTo: containerView.centerXAnchor))!,
            (userTextField.widthAnchor.constraint(equalTo: containerView.widthAnchor, multiplier: 0.8))!,
            userTextField.topAnchor.constraint(equalTo: containerView.topAnchor, constant: containerView.frame.size.height * 0.15),
            userTextField.heightAnchor.constraint(equalToConstant: 40)
            ])

```

I expect the topAnchor of my `UITextField` to appear similar across all devices at 0.15 the height of it container view but what I'm getting is 0