UIKit has had UITraitCollection for a while now. Since iOS 9 you could use UITraitCollection to see whether the device supports 3D Touch (a sad conversation for another day)
In iOS 12, UITraitCollection got a new property: var userInterfaceStyle: UIUserInterfaceStyle
which supports three cases: light
, dark
, and unspecified
Since UIViewController inherits UITraitEnvironment, you have access to the ViewController's traitCollection
. This stores userInterfaceStyle
.
UITraitEnviroment also has some nifty protocol stubs that help your code interpret when state changes happen (so when a user switches from the Dark side to the Light side or visa versa). Here's a nice coding example for you:
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
if self.traitCollection.userInterfaceStyle == .dark {
// User Interface is Dark
} else {
// User Interface is Light
}
}
override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
// Trait collection has already changed
}
override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
// Trait collection will change. Use this one so you know what the state is changing to.
}
}