How to make a UITextView fill up the remaining space

Question

I have a UIButton and UITextField side by side as follows.

I want the Add button to only have a width based on the content. And the text view shall take up the rest of the space. I have the following auto layout constraints.

private func setupLayout() {
    newDeviceIdTextField.topAnchor.constraint(equalTo: deviceIdLabel.bottomAnchor, constant: 12).isActive = true
    newDeviceIdTextField.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 12).isActive = true

    newDeviceIdButton.topAnchor.constraint(equalTo: deviceIdLabel.bottomAnchor, constant: 12).isActive = true
    newDeviceIdButton.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -12).isActive = true
    newDeviceIdButton.leadingAnchor.constraint(equalTo: newDeviceIdTextField.trailingAnchor, constant: 0).isActive = true
}

In this article there is a section which I believe exactly solves my problem. But I just don't understand how.

What am I missing here?

Answer 1

A button automatically sizes its width to fit its content, and both a text field and a button have an automatic height. So what you want to do is trivial:

Pin the left of the text field where you want it.

Pin the right of the button where you want it.

Pin the tops of both where you want them.

Pin the right of the text field to the left of the button and set that constant to a small number such as 8.