Access container view child properties swift

Question

What I want to achieve:

User presses the button in the ViewController then, the color of the button placed in the container view should change its color to red.

Answer 1

Swift 4, Xcode 9.4.1

var contentViewController : UIContentViewController?

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == containerSegueName {
       contentViewController = segue.destination as? UIContentViewController
    }
}

Answer 2

I recommend not to rely on segue.identifier, but rather test for destination type directly:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    super.prepare(for: segue, sender: sender)

    if let vc = segue.destination as? YourViewController {
        vc.someVariable = true
    }
}

This way you avoid mistakes with a misspelled segue name.

Answer 3

Step by step:

1. Name the segue between your view controller and container view controller.
2. Add a property to your view controller which will contain the container view controller.
3. In your view controller implement a method prepareForSegue(_:sender:).
4. In the method check if segue.identifier equals the identifier you specified in step 1.
5. If true, then save the segue.destinationViewController to your property from step 2.
6. Now you have the container view controller stored in your property so you can do customization from your class. You should have the view controller stored in viewDidLoad() method already.

Example:

var containerViewController: YourContainerViewControllerClass?
let containerSegueName = "testSegue"
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == containerSegueName {
        containerViewController = segue.destinationViewController as? YourContainerViewControllerClass
    }
}

Answer 4

Swift 3 for macOS:

// MARK: - Container View Controller

var containerViewController: ContainerViewController?

let containerSegueIdentifier = "Container Segue"

override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
    if segue.identifier == containerSegueIdentifier {
        if let connectContainerViewController = segue.destinationController as? FormationViewController {
            formationViewController = connectContainerViewController
        }
    }
}

Check identifier and controller class.