Adapter Pattern

• You use this pattern to convert the interface of class to a different form that matches what we need

Classical Structure

Scenario

• Add filters to photo

Problem

• Interface of caramel class doesn't match what apply method of ImageView expects because Apply method expects class that implements IFilter.

public class Image
{
}
public interface IFilter
{
    void Apply(Image image);
}
public class VividFilter : IFilter
{
    public void Apply(Image image)
    {
        Console.WriteLine("Applying vivid filter");
    }
}
public class ImageView
{
    private readonly Image image;

    public ImageView(Image image)
    {
        this.image = image;
    }

    public void Apply(IFilter filter)
    {
        filter.Apply(image);
    }
}
public class Caramel
{
    public void Init() { }

    public void Render(Image image)
    {
        Console.WriteLine("Applying caramel filter");
    }
}

Solution

• CaramelFilter is the adapter and Caramel is the adaptee
• Composition is better than inheritance

public class CaramelFilter : IFilter
{
    private Caramel caramel;
    public CaramelFilter(Caramel caramel)
    {
        this.caramel = caramel;
    }
    public void Apply(Image image)
    {
        caramel.Init();
        caramel.Render(image);
    }
}

Example Structure

Example Code