The Facade pattern is a design principle that simplifies the interface of a complex system or subsystem. It provides a single point of access to a set of functionalities that are otherwise scattered and hard to use. In this article, you will learn how to use the Facade pattern in Dart, a modern and expressive programming language for app development.
The Facade pattern can offer several advantages in your app development process, such as reducing complexity and coupling, improving modularity and flexibility, and enhancing usability and reusability. By hiding the details and dependencies of the subsystems, you can make your code more readable, maintainable, and testable. Furthermore, encapsulating the subsystems behind a facade allows you to change or replace them without affecting the rest of the code. Additionally, providing a simple and consistent interface makes your app easier to use and reuse by different clients or components.
Facade is particularly useful when integrating new code with existing, possibly legacy systems. It shields the new code from the intricacies of the legacy codebase.
Facade is an object that serves as a front-facing interface masking more complex underlying or structural code and they provide a unified and simplified interface to a set of interfaces in a subsystem, therefore it hides the complexities of the subsystem from the client
In order to implement the Facade pattern in Dart, you must first identify the subsystems which provide the functionalities you wish to expose. These can be classes, libraries, packages, or modules that perform specific tasks or operations. Afterwards, create a facade class which acts as a wrapper or proxy for the subsystems. It should have methods that delegate calls to the appropriate subsystems and handle errors or exceptions that may occur. Finally, use the facade class in your app logic instead of directly interacting with the subsystems. The facade should provide an interface that meets your app requirements and expectations.
create one or more Concrete Strategy objects that implement the Strategy interface. Finally, you set the Strategy object for the Context object by calling its setStrategy() method.
To illustrate the Facade pattern in Dart, let's explore how it can be used in app development. For instance, you can use the Facade pattern to simplify the interaction with a database. By creating a facade class that wraps the database class and exposes only the methods that are relevant for your app, such as getProducts, addOrder, and deleteCustomer, you can avoid dealing with the low-level details and complexities of the database class. Additionally, using the Facade pattern to abstract the communication with a web service is another example. By creating a facade class that wraps the web service class and exposes only methods such as fetchNews, postComment, and likeArticle, you can simplify the interaction with the web service class and handle network and data issues all in one place.
When we have to start a computer, all we have to do is press the start button. We really do not care what all things go inside the computer hardware and software. It is an example of Facade pattern
The Facade pattern can make your app easier to test, as you can isolate the subsystems from the app logic, and mock or stub them as needed. To test the Facade pattern in Dart, you should use unit tests to verify the behavior and functionality of the facade class and the subsystems. The dart:test package is great for writing and running your unit tests, and you can use dart:mockito to create mock objects for the subsystems. Additionally, integration tests are great for checking the interaction and integration of the facade class and the subsystems. The dart:integration_test package is useful for writing and running your integration tests, while dart:http can be used to simulate web service requests and responses. Finally, widget tests are perfect for validating the user interface and user experience of your app. The flutter_test package is great for writing and running your widget tests, while flutter_driver is perfect for performing automated UI testing.
The Facade pattern is a powerful and useful design principle, but it also has some pitfalls and challenges. Therefore, when using the Facade pattern in Dart, it is important to practice certain best practices. To avoid creating a god object that violates the single responsibility principle, create multiple facades that each focus on a specific aspect or feature of your app. Additionally, ensure that the facade adds value and functionality to your app - such as error handling, caching, logging, or validation - rather than becoming a redundant layer that adds unnecessary overhead and duplication. Furthermore, use dependency injection or inversion of control to decouple the facade from the subsystems and make them interchangeable and testable.