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DELEGATES - Coggle Diagram

DELEGATES

EXAMPLE

Non Extensible Code

PhotoProcessor

public class PhotoProcessor
{
    public void Process(string path)
    {
        var photo = Photo.Load(path);

        var filters = new PhotoFilters();
        filters.ApplyBrightness(photo);
        filters.ApplyContrast(photo);
        filters.Resize(photo);

        photo.Save();
    }
}

Photo

public class Photo
{
    public static Photo Load(string path)
    {
        return new Photo();
    }

    public void Save()
    {

    }
}

Non Extensible Code

PhotoProcessor

public class PhotoProcessor
{
    // access / delegate / return type / name (params)
    public delegate void PhotoFilterHandler(Photo photo);


    public void Process(string path, PhotoFilterHandler filterHandler)
    {
        var photo = Photo.Load(path);

        // the delegate will apply the filter for us
        filterHandler(photo);

        photo.Save();
    }

}

CLIENT CODE

internal class Program
{
    public static void Main(string[] args)
    {
        var photoProcessor = new PhotoProcessor();
        // This class provides us with filters
        var photoFilters = new PhotoFilters();

        // We can add a pointer to a method
        PhotoProcessor.PhotoFilterHandler filterHandler = photoFilters.ApplyBrightness;
        filterHandler += photoFilters.ApplyContrast;
        filterHandler += RemoveRedEyes;

        // We pass the delegate instance with the method
        photoProcessor.Process("path", filterHandler);
    }

    static void RemoveRedEyes(Photo photo)
    {
        Console.WriteLine("APPLY REMOVE RED EYE");
    }

}

PhotoFilters

public class PhotoFilters
{
    public void ApplyBrightness(Photo photo)
    {
        Console.WriteLine("APPLY BRIGHTNESS");
    }

    public void ApplyContrast(Photo photo)
    {
        Console.WriteLine("APPLY CONTRAST");
    }

    public void Resize(Photo photo)
    {
        Console.WriteLine("APPLY RESIZE");
    }
}

Photo

public class Photo
{
    public static Photo Load(string path)
    {
        return new Photo();
    }

    public void Save()
    {

    }
}