Explain the techniques for implementing navigation and data passing between screens in a Swift app.

Implementing navigation and data passing between screens is a fundamental aspect of building Swift applications with multiple views or screens. There are several techniques available to handle navigation and data passing effectively. Let's explore some of the commonly used techniques:

1. Segues:

* Segues provide a visual way to define the flow of navigation between view controllers in Interface Builder.
* Create segues between view controllers by control-dragging from a UI element, such as a button, to the destination view controller. Assign an identifier to the segue and optionally configure its transition style.
* To pass data between view controllers using segues, override the `prepare(for:sender:)` method in the source view controller. Access the destination view controller using the `segue.destination` property and set the required data in its properties.
2. Programmatically Instantiated View Controllers:

* In certain scenarios, you may need to programmatically create and present view controllers without using segues.
* Instantiate the destination view controller using its class initializer. Set any necessary data properties before presenting or pushing the view controller onto the navigation stack.
* To navigate back or dismiss the presented view controller, use methods like `dismiss(animated:completion:)`, `popViewController(animated:)`, or `popToRootViewController(animated:)`.
3. Navigation Controller:

* The `UINavigationController` class provides a built-in navigation stack to manage hierarchical navigation between view controllers.
* Embed the initial view controller in a navigation controller in Interface Builder or programmatically using the `UINavigationController` initializer.
* Push view controllers onto the navigation stack using methods like `pushViewController(_:animated:)`. To navigate back, use methods like `popViewController(animated:)` or the navigation bar's back button.
4. Delegate Pattern:

* The delegate pattern allows communication between view controllers by defining a protocol that the source view controller conforms to, and the destination view controller acts as the delegate.
* Define a delegate protocol in the source view controller, specifying methods that the delegate should implement.
* Set the destination view controller's delegate property to the source view controller. When required, call the delegate methods to pass data or trigger actions in the source view controller.
5. Singleton or Shared Data Manager:

* Create a singleton or shared data manager class to store and manage shared data across different view controllers.
* This technique involves creating a class with shared data properties and methods, which can be accessed from any view controller in the app.
* View controllers can read and modify the shared data manager's properties to exchange data between screens.
6. Notifications:

* Notifications provide a way to broadcast and handle events throughout an application, including passing data between view controllers.
* Post a notification with a specific name and optional data from the source view controller using the `NotificationCenter.default.post(name:object:userInfo:)` method.
* Register to observe the notification in the destination view controller using the `NotificationCenter.default.addObserver(_:selector:name:object:)` method. Implement a method that will be called when the notification is posted and retrieve the passed data.

These techniques offer flexibility and control when implementing navigation and data passing between screens in Swift applications. You can choose the technique that best suits your app's architecture, complexity, and data flow requirements. By effectively managing navigation and data passing, you can create seamless and engaging user experiences across multiple screens in your Swift app.