Initiates the update process for a layer if it is currently marked as needing an update.
- iOS 3.0+
- macOS 10.6+
- tvOS 9.0+
- Core Animation
You can call this method as needed to force an update to your layer’s contents outside of the normal update cycle. Doing so is generally not needed, though. The preferred way to update a layer is to call
set and let the system update the layer during the next cycle.