The Facade Pattern is a structural design pattern that provides a simplified interface to a complex subsystem. It helps to hide the complexities of the system and provides an easy-to-use interface to the client.
Imagine you have an online restaurant system where customers can place orders, and the orders need to be processed and shipped. Without a unified interface, the client code has to interact with multiple subsystems (e.g., restaurant and shipping service) directly, making the code complex and difficult to maintain.
The Facade Pattern helps solve this problem by providing a unified interface to the complex subsystem. In this example, a Facade class is created to provide a simple interface for placing orders and handling the shipping process, hiding the complexities of interacting with each subsystem.
- Identify the Subsystems: Identify the various subsystems that need to be used together (e.g., restaurant and shipping service).
- Create the Facade: Create a facade class that provides a simplified interface to the subsystems.
- Delegate Calls: The facade class should delegate the calls to the appropriate subsystems to perform the task.
- Order Class: Represents an order placed by a customer.
- Restaurant Class: Handles adding orders to the cart and completing orders.
- Shipping Service Class: Handles accepting orders, calculating shipping expenses, and shipping orders.
- Facade Class: Provides a simplified interface to the restaurant and shipping service.
The main function demonstrates how to use the Facade to place orders and handle the shipping process.
Adding order to cart: Chicken with rice
Adding order to cart: Sushi
Completing orders...
Order accepted: Chicken with rice
Calculating shipping expenses...
Shipping order: Chicken with rice
Order accepted: Sushi
Calculating shipping expenses...
Shipping order: Sushi
Adding order to cart: Chicken with rice
Adding order to cart: Sushi
Completing orders...
Order accepted: Chicken with rice
Calculating shipping expenses...
Shipping order: Chicken with rice
Order accepted: Sushi
Calculating shipping expenses...
Shipping order: Sushi- Simplified Interface: Provides a - simplified interface to a complex subsystem.
- Reduced Complexity: Hides the complexities of the subsystem from the client.
- Improved Code Maintenance: Changes in the subsystem do not affect the client code.
Tutorial Link: https://code-maze.com/facade/
The tutorial at Code Maze provides a great example of the Facade Pattern. I recommend readers to check their tutorial for better learning!