What is a segue?

Swift version: 5.6

Paul Hudson @twostraws May 28th 2019

Segues are visual connectors between view controllers in your storyboards, shown as lines between the two controllers. They allow you to present one view controller from another, optionally using adaptive presentation so iPads behave one way while iPhones behave another.

When a segue is triggered – perhaps through a button press or a table view selection – the prepare(for:) method will be called on your view controller, at which point you can configure your destination view controller by setting some properties.

For example, you might write something like this in response to a table view selection:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    guard let selectedPath = tableView.indexPathForSelectedRow else { return }
    if let target = segue.destination as? UserViewController {
        target.selectedUser = selectedPath.row
    }
}

That finds the row that was tapped, typecasts the destination to be a UserViewController, then tells it which row was selected.