UITextView that expands to text using auto layout

Summary: Disable scrolling of your text view, and don't constraint its height.

To do this programmatically, put the following code in viewDidLoad:

let textView = UITextView(frame: .zero, textContainer: nil)
textView.backgroundColor = .yellow // visual debugging
textView.isScrollEnabled = false   // causes expanding height
view.addSubview(textView)

// Auto Layout
textView.translatesAutoresizingMaskIntoConstraints = false
let safeArea = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
    textView.topAnchor.constraint(equalTo: safeArea.topAnchor),
    textView.leadingAnchor.constraint(equalTo: safeArea.leadingAnchor),
    textView.trailingAnchor.constraint(equalTo: safeArea.trailingAnchor)
])

To do this in Interface Builder, select the text view, uncheck Scrolling Enabled in the Attributes Inspector, and add the constraints manually.

Note: If you have other view/s above/below your text view, consider using a UIStackView to arrange them all.

Here's a solution for people who prefer to do it all by auto layout:

In Size Inspector:

1. Set content compression resistance priority vertical to 1000.

2. Lower the priority of constraint height by click "Edit" in Constraints. Just make it less than 1000.

In Attributes Inspector:

1. Uncheck "Scrolling Enabled"