Facade (Front)

• Use this pattern to provide a simple interface to a complex system
• Facade reduces coupling

Classical Structure

Scenario

• Sending push notifications to users

Problem

• Everytime to send a push notification you have to follow lot of steps.
• Main class is coupled or dependent on these classes (AuthToken, Connection, Message, NotificationServer) for sending notification
• If other classes need to send notification, they also are coupled to these classes
• If any of these classes change several classes might be affected.

public class Connection
{
    public void Disconnect()
    {

    }
}
public class AuthToken
{
}
public class Message
{
    private readonly string content;

    public Message(string content)
    {
        this.content = content;
    }
}
public class NotificationServer
{
    public Connection Connect(string ipAddress)
    {
        return new Connection();
    }

    public AuthToken Authenticate(string appID, string key)
    {
        return new AuthToken();
    }

    public void Send(AuthToken token, Message message, string target) 
    {
        Console.WriteLine("Sending a message");
    }
}
public class Program
{
	public static void Main()
	{
		    var server = new NotificationServer();
            var connection = server.Connect("ip");
            var authToken = server.Authenticate("AppId", "key");
            var message = new Message("Hello World");
            server.Send(authToken, message, "target");
            connection.Disconnect();
	}
}

Solution

• Encapsulates all logic to send push notification
• Hide all complexity behind facade

public class NotificationService
{
    public void Send(string message, string target)
    {
        var server = new NotificationServer();
        var connection = server.Connect("ip");
        var authToken = server.Authenticate("AppId", "key");
        server.Send(authToken, new Message(message), target);
        connection.Disconnect();
    }
}
public class Program
{
	public static void Main()
	{
		var service = new NotificationService();
		service.Send("Hello World", "target");
	}
}

Example Code