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Removing views from a UIStackView with removeArrangedSubview()

That was a long chapter, and I hope you learned a lot. But you deserve a break, so I have some good news: it's trivial to remove views from a UIStackView. Heck, at its simplest it's just a matter of telling removeArrangedSubview() which view you don’t want then removing that view from its superview – the others are automatically resized and re-arranged to fill the space.

However, using removeArrangedSubview() doesn’t remove the view altogether – it keeps the view in memory, which is helpful if you plan to re-add it later on because you can avoid recreating it. Here, though, we actually want to remove the web view and destroy it entirely, and that can be done with a call to removeFromSuperview() instead.

In this particular project, we need to do a little more:

  • We want the delete button to work only if there's a web view selected.
  • We want to find the location of the active web view inside the stack view, then remove it.
  • If there are now no more web views, we want to call setDefaultTitle() to reset the user interface.
  • We need to find whatever web view immediately follows the one that was removed.
  • We then make that the new selected web view, highlighting it in blue.

We already pointed the delete button at a method called deleteWebView(), so all you need to do is plug this in. I've added comments to make sure it's all clear:

@objc func deleteWebView() {
    // safely unwrap our webview
    if let webView = activeWebView {
        if let index = stackView.arrangedSubviews.firstIndex(of: webView) {
            // We found the webview – remove it from the stack view and destroy it
            webView.removeFromSuperview()

            if stackView.arrangedSubviews.count == 0 {
                // go back to our default UI
                setDefaultTitle()
            } else {
                // convert the Index value into an integer
                var currentIndex = Int(index)

                // if that was the last web view in the stack, go back one
                if currentIndex == stackView.arrangedSubviews.count {
                    currentIndex = stackView.arrangedSubviews.count - 1
                }

                // find the web view at the new index and select it
                if let newSelectedWebView = stackView.arrangedSubviews[currentIndex] as? WKWebView {
                    selectWebView(newSelectedWebView)
                }
            }
        }
    }
}

So, although the act of removing a view from a UIStackView is just a matter of calling either removeArrangedSubview() or removeFromSuperview() depending on whether you want to use it again, we need to do a little more to make sure the user interface updates correctly.

The last thing we're going to do is talk about multitasking on iPad, and add a few user interface clean ups to make the project complete…

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