Introducing the Facade design pattern

Design patterns are proven solutions to software design problems. They help improve code quality, promote reusability, and increase maintainability. We use them to save time and produce quality, extensible and flexible code. In this article, we are going to introduce the Facade design pattern.

The Facade design pattern is a structural design pattern that provides a simple interface to a complex set of classes, interfaces, and objects. This pattern hides the complexity of the system and provides a single entry point to access the system.

There are several key elements in the Facade pattern:

• Facade: A class that provides a simple interface to a complex system and delegates incoming requests to the appropriate objects in the system.
• Subsystem: A set of classes that implement system functionality. The Facade class will deal with these classes.
• Client: The piece of code that uses Facade to access the system.

The Facade pattern allows you to simplify interaction with a complex system by providing a single entry point. This pattern can be useful when you have a complex system with many classes and objects that you want to expose the details of the system.

Here is a simple example of the Facade pattern in C#:

// Subsystem classes
class SubsystemA
{
    public void MethodA()
    {
       Console.WriteLine("SubsystemA Method");
    }
}
class SubsystemB
{
    public void MethodB()
    {
       Console.WriteLine("SubsystemB Method");
    }
}
// Facade class
class Facade
{
    private readonly SubsystemA subsystemA;
    private readonly SubsystemB subsystemB;
    public Facade()
    {
        subsystemA = new SubsystemA();
        subsystemB = new SubsystemB();
    }
    public void Operation()
    {
       subsystemA.MethodA();
        subsystemB.MethodB();
    }
}
// Client code
class Client
{
    static void Main()
    {
        Facade facade = new Facade();
        facade.Operation();
    }
}

In this example, the SubsystemA and SubsystemB classes implement the functionality of a complex system. The Facade class provides a simple interface to the system by calling the appropriate methods. The Client code creates an instance of the Facade class and calls the Operation method to interact with the system. The output of the program after calling the Operation method will be as follows:

SubsystemA Method
SubsystemB Method

Which shows that Facade is able to call methods of Subsystem classes and provides a simple interface to use.

To read about other design patterns, you can use the list below. There is also a code repository on GitHub that includes all the design patterns.