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Facade Pattern

Facade Pattern 


Gamma Categorization: Structural Design Pattern
Summary: Provide a unified interface to a set of interfaces in a subsystem. Façade defines a higher-level interface that makes the subsystem easier to use.

Sample Code

Problem: We want a facade for our digital camera subsystems.

public class DigitalCameraFacade
{
    ICamera camera;        
    IStorageManager storageManager;
    INetworkManager networkManager;

    public DigitalCameraFacade(ICamera camera, IStorageManager storageManager, INetworkManager networkManager)
    {
        this.camera = camera;            
        this.storageManager = storageManager;
        this.networkManager = networkManager;
    }

    public void TakePhoto()
    {
        var photo = camera.TakePhoto();
        storageManager.WriteFile(photo);
        networkManager.Send(photo);
    }
}

public interface ICamera
{
    byte[] TakePhoto();
}

public class DSLR : ICamera
{
    public byte[] TakePhoto()
    {
        System.Console.WriteLine("Taking photo.");
        return new byte[1024];
    }
}

public interface IStorageManager
{
    byte[] ReadFile();
    void WriteFile(byte[] file);        
}

public class SDCardManager : IStorageManager
{
    public byte[] ReadFile()
    {
        System.Console.WriteLine("Reading file to drive.");
        return new byte[1024];
    }
    public void WriteFile(byte[] file) => System.Console.WriteLine("Writing file from drive.");
}

public interface INetworkManager
{
    void Connect();
    void Send(byte[] file);
}

public class WifiManager : INetworkManager
{
    public void Connect() => System.Console.WriteLine("Connecting.");
    public void Send(byte[] file) => System.Console.WriteLine("Sending file.");
}

Usage

var digitalCamera = new DigitalCameraFacade(new DSLR(), new SDCardManager(), new WifiManager());
digitalCamera.TakePhoto();

Output

Taking photo.
Writing file from drive.
Sending file.

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