Decorator

• Use this pattern to add additional behavior to an object

Classical Structure

Scenario

• Store data in cloud

Problem

• For every feature we are adding we need to create various classes combining these features

public class CloudStream
{
    public virtual void Write(string data)
    {
        Console.WriteLine("Storing " + data);
    }
}
public class EncryptedCloudStream: CloudStream
{
    public override void Write(string data)
    {
        var encrypted = Encrypt(data);
        base.Write(encrypted);
    }

    private string Encrypt(string data)
    {
        return "!@#$%^^&&*";
    }
}
public class CompressedCloudStream: CloudStream
{
    public override void Write(string data)
    {
        var compressed = Compress(data);
        base.Write(compressed);
    }

    private string Compress(string data)
    {
        return data.Substring(0, 5);
    }
}
public class CompressedAndEncryptedCloudStream: CloudStream
{
    public override void Write(string data)
    {
        var compressed = Compress(data);
        var encrypted = Encrypt(compressed);
        base.Write(encrypted);
    }

    private string Compress(string data)
    {
        return data.Substring(0, 5);
    }

    private string Encrypt(string data)
    {
        return "!@#$%^^&&*";
    }
}

Solution

public interface IStream
{
    void Write(string data);
}
public class CloudStream: IStream
{
    public virtual void Write(string data)
    {
        Console.WriteLine("Storing " + data);
    }
}
public class CompressedCloudStream: IStream
{
    private readonly IStream _stream;

    public CompressedCloudStream(IStream stream)
    {
        _stream = stream;
    }

    public void Write(string data)
    {
        var compressed = Compress(data);
        _stream.Write(compressed);
    }

    private string Compress(string data)
    {
        return data.Substring(0, 5);
    }
}
public class EncryptedCloudStream: IStream
{
    private IStream _stream;

    public EncryptedCloudStream(IStream stream)
    {
        _stream = stream;
    }

    public void Write(string data)
    {
        var encrypted = Encrypt(data);
        _stream.Write(encrypted);
    }

    private string Encrypt(string data)
    {
        return "!@#$%^^&&*";
    }
}
public class Program
{
	public static void Main()
	{
		var stream = new EncryptedCloudStream(new CompressedCloudStream(new CloudStream()));
		stream.Write("sensitive data");
	}
}

Example Structure

Example Code