Dark mode has gradually become a staple feature in modern operating systems, including Apple's iOS and iPadOS. It provides a darker color scheme that's visually soothing, especially in low-light environments, and may even have a notable impact on device battery life. Developers of iOS applications often need to determine whether dark mode is enabled to adjust the app's user interface accordingly. This article will delve into the process of checking whether dark mode is enabled on iOS and iPadOS, providing technical insights and practical examples.

How Dark Mode Works

At its core, dark mode in iOS/iPadOS is a system-wide appearance setting that changes the color scheme of the user interface to dark. Apple's method is a complementary approach where applications automatically adapt their interface based on this system setting if they properly support dynamic system appearance.

Key Concepts

• Traits System: iOS uses a `traitCollection` to manage different interface style changes, among other traits. A `UITraitCollection` object encapsulates the attributes of the interface's environment, such as display scale, horizontal and vertical size classes, and user interface style (light or dark).
• User Interface Style: An aspect of `UITraitCollection`, it determines the interface appearance. In code, this can be accessed using the property `userInterfaceStyle`. It provides values like `.light`, `.dark`, and `.unspecified`.

Checking Dark Mode Status Programmatically

To determine whether dark mode is enabled, developers can take advantage of the `UITraitCollection`. Below are examples and explanations regarding how this can be implemented both within a `UIViewController` and throughout an entire app using different methodologies.

Example: Checking in a `UIViewController`

In a sample view controller, you can override the function `traitCollectionDidChange(_:)`. This method allows you to respond to changes in the environment traits, such as when your app moves from light to dark mode or vice versa.

• Supporting Both Modes: To implement and support both light and dark modes seamlessly, ensure that your colors, images, and other assets adapt to these changes. Utilize asset catalogs to provide light and dark variants of images and colors.
• Dynamic Type: If your app uses dynamic type, ensure text scales and adjusts properly in both modes by adapting text and background colors for readability.
• Animation: Consider smooth transitions for user experience when the interface style changes, as abrupt changes can be jarring.