generics

Author: T0shik

Generics/mediatr_parody.linq

@@ -0,0 +1,59 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	var handler = new RequestHandler();
+	handler.Handle(new GetAge()).Dump();
+	handler.Handle(new GetName()).Dump();
+}
+
+public interface IRequest<T> { }
+
+public class GetAge : IRequest<int> { }
+
+public class GetName : IRequest<string> { }
+
+public interface IHandler { };
+
+public abstract class Handler<T> : IHandler { 
+	public abstract T Handle(IRequest<T> request);
+};
+
+public abstract class Handler<TRequest, TResponse> : Handler<TResponse>
+	where TRequest : IRequest<TResponse>
+{
+	public override TResponse Handle(IRequest<TResponse> request) => 
+		Handle((TRequest) request);
+	
+	protected abstract TResponse Handle(TRequest requst);
+}
+
+public class GetAgeHandler : Handler<GetAge, int>
+{
+	protected override int Handle(GetAge request) => 20;
+}
+
+public class GetNameHandler : Handler<GetName, string>
+{
+	protected override string Handle(GetName request) => "Foo";
+}
+
+
+public class RequestHandler
+{
+	public Dictionary<Type, IHandler> requestHandlers = new() {
+		[typeof(GetAge)] = new GetAgeHandler(),
+		[typeof(GetName)] = new GetNameHandler(),
+	};
+
+	public T Handle<T>(IRequest<T> request)
+	{
+		var handler = requestHandlers[request.GetType()];
+		if (handler is Handler<T> h) {
+			return h.Handle(request);
+		}
+		return default;
+	}
+}
+
+

Generics/no_generics.linq

@@ -0,0 +1,46 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	Hasher.Hash(new Post()).Dump();
+	Hasher.Hash(new Comment()).Dump();
+}
+
+public class Content
+{
+	public string Id { get; set; } = "id";
+	public string Author { get; set; } = "author";
+	public string Text { get; set; } = "text";
+}
+
+public class Post : Content { }
+
+public class Comment : Content
+{
+	public string PostId { get; set; } = "postid";
+}
+
+public class ContentHashingStrategy
+{
+	public static int Hash(Post post) =>
+		post.Text.Length
+		+ post.Author.Length;
+}
+
+public class CommentHashingStrategy
+{
+	public static int Hash(Comment comment) =>
+		comment.Text.Length
+		+ comment.Author.Length
+		+ comment.PostId.Length;
+}
+
+public class Hasher
+{
+	public static int Hash(Content content)
+	{
+		if (content is Post p) return ContentHashingStrategy.Hash(p);
+		if (content is Comment c) return CommentHashingStrategy.Hash(c);
+		return 0;
+	}
+}

Generics/with_generics.linq

@@ -0,0 +1,57 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	Hasher.Hash(new Post()).Dump();
+	Hasher.Hash(new Comment()).Dump();
+}
+
+public interface IHashingStrategy
+{
+	int Hash(Content content);
+}
+
+public class Content
+{
+	public string Id { get; set; } = "id";
+	public string Author { get; set; } = "author";
+	public string Text { get; set; } = "text";
+}
+
+public class Content<T> : Content where T : IHashingStrategy { }
+
+public class Post : Content<ContentHashingStrategy> { }
+
+public class Comment : Content<CommentHashingStrategy>
+{
+	public string PostId { get; set; } = "postid";
+}
+
+public class ContentHashingStrategy : IHashingStrategy
+{
+	public int Hash(Content content)
+	{
+		return content.Text.Length
+			+ content.Author.Length;
+	}
+}
+
+public class CommentHashingStrategy : IHashingStrategy
+{
+	public int Hash(Content content)
+	{
+		var comment = content as Comment;
+		return comment.Text.Length
+			+ comment.Author.Length
+			+ comment.PostId.Length;
+	}
+}
+
+public class Hasher
+{
+	public static int Hash<T>(Content<T> content)
+		where T : IHashingStrategy, new()
+	{
+		return Activator.CreateInstance<T>().Hash(content);
+	}
+}

Generics/with_generics_extended.linq

@@ -0,0 +1,63 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	Hasher.Hash(new Post()).Dump();
+	Hasher.Hash(new Comment()).Dump();
+}
+
+public interface IHashingStrategy {
+	int Hash(Content content);
+}
+
+public abstract class HashingStrategy<T> : IHashingStrategy
+	where T : Content 
+{
+	public int Hash(Content content) => Hash((T) content);
+
+	protected abstract int Hash(T content);
+}
+
+public class Content
+{
+	public string Id { get; set; } = "id";
+	public string Author { get; set; } = "author";
+	public string Text { get; set; } = "text";
+}
+
+public class Content<T> : Content where T : IHashingStrategy, new() {}
+
+public class Post : Content<ContentHashingStrategy> { }
+
+public class Comment : Content<CommentHashingStrategy>
+{
+	public string PostId { get; set; } = "postid";
+}
+
+public class ContentHashingStrategy : HashingStrategy<Post>
+{
+	protected override int Hash(Post content)
+	{
+		return content.Text.Length
+			+ content.Author.Length;
+	}
+}
+
+public class CommentHashingStrategy : HashingStrategy<Comment>
+{
+	protected override int Hash(Comment comment)
+	{
+		return comment.Text.Length
+			+ comment.Author.Length
+			+ comment.PostId.Length;
+	}
+}
+
+public class Hasher
+{
+	public static int Hash<H>(Content<H> content)
+		where H : IHashingStrategy, new()
+	{
+		return Activator.CreateInstance<H>().Hash(content);
+	}
+}

README.md

@@ -14,4 +14,5 @@ Full Playlist can be found [here](https://www.youtube.com/playlist?list=PLOeFnOV
 - [IEnumerable](https://youtu.be/at6weLnskpU)
 - [Reflection](https://youtu.be/cdG2JxuZvNI)
 - [Expression Trees](https://youtu.be/dwr40KytyaY)
-- [Delegates (+Func +Action +Closure)](https://youtu.be/KaxNwGA9fiY)
+- [Delegates (+Func +Action +Closure)](https://youtu.be/KaxNwGA9fiY)
+- [Generics](https://youtu.be/Q1Tv7vj3Txo)