What is a delegate in UIKit

A delegate in UIKit is a design pattern that allows one object to communicate back to another object when certain events occur. This pattern is commonly used to handle events and actions in a decoupled way, where one object (the delegate) implements methods to respond to events that happen in another object (the delegator).

For example, in UIKit, gesture recognizers can use delegates to handle gesture events. The delegate methods are called when specific gestures are recognized, allowing the delegate to respond appropriately.

In the context of concurrency, it's important to understand the threading guarantees provided by the delegate methods. Some delegates guarantee that their callbacks will always be on the main thread, which is crucial for updating the UI safely. However, other delegates may not provide such guarantees, requiring the developer to ensure thread safety manually.

For more details on delegate callbacks and concurrency, you can refer to the session Migrate your app to Swift 6 (19:29).