decorator & proxy

Author: T0shik

README.md

@@ -4,8 +4,20 @@ This repository is a collection of my one off tutorials about asp.net core tooki
 Full Playlist can be found [here](https://www.youtube.com/playlist?list=PLOeFnOV9YBa4ary9fvCULLn7ohNKR6Ees).
 
 ## Table of contents
+
+### Creational Patterns
+
 - [Factory, Abstract Factory, Factory Method](https://youtu.be/xN7EFHU_rXA)
 - [Builder](https://youtu.be/WfBsYo20D_I)
 - [Prototype](https://youtu.be/fqaoCDyxb1w)
 - [Singleton](https://youtu.be/9_9hI69fwhg)
-- [Adapter](https://youtu.be/9ZFN8DrvcYA)
+
+### Structural Patterns
+
+- [Adapter](https://youtu.be/9ZFN8DrvcYA)
+- [Decorator](https://youtu.be/6rTnCkdbJA4)
+- [Proxy](https://youtu.be/m0aXyRDEQqU)
+
+
+### Behavioral Patterns
+WIP

decorator/distributed_cache_example.linq

@@ -0,0 +1,48 @@
+<Query Kind="Program">
+  <NuGetReference>Microsoft.Extensions.Caching.Abstractions</NuGetReference>
+  <Namespace>Microsoft.Extensions.Caching.Distributed</Namespace>
+  <Namespace>System.Threading.Tasks</Namespace>
+</Query>
+
+void Main()
+{
+
+}
+
+public class KeyPrefixedCache : IDistributedCache
+{
+	IDistributedCache _cache;
+	string _prefix;
+
+	public KeyPrefixedCache(IDistributedCache cache, string prefix)
+	{
+		_cache = cache;
+		_prefix = prefix;
+	}
+
+	private string PrefixKey(string key) => $"{_prefix}_{key}";
+
+	public byte[] Get(string key) =>
+		_cache.Get(PrefixKey(key));
+
+	public Task<byte[]> GetAsync(string key, CancellationToken token = default) =>
+		_cache.GetAsync(PrefixKey(key), token)
+
+	public void Refresh(string key) =>
+		_cache.Refresh(PrefixKey(key));
+
+	public Task RefreshAsync(string key, CancellationToken token = default) =>
+		_cache.RefreshAsync(PrefixKey(key), token);
+
+	public void Remove(string key) =>
+		_cache.Remove(PrefixKey(key));
+
+	public Task RemoveAsync(string key, CancellationToken token = default) =>
+		_cache.RemoveAsync(PrefixKey(key), token)
+
+	public void Set(string key, byte[] value, DistributedCacheEntryOptions options) =>
+		_cache.Set(PrefixKey(key), value, options);
+
+	public Task SetAsync(string key, byte[] value, DistributedCacheEntryOptions options, CancellationToken token = default) =>
+		_cache.SetAsync(PrefixKey(key), value, options, token);
+}

decorator/example.linq

@@ -0,0 +1,54 @@
+<Query Kind="Program" />
+
+void Main()
+{
+
+}
+
+public interface IDumbData
+{
+	int Id { get; set; }
+	string Name { get; set; }
+	string Description { get; set; }
+}
+
+public class DumbData : IDumbData
+{
+	public int Id { get; set; }
+	public string Name { get; set; }
+	public string Description { get; set; }
+}
+
+public abstract class BaseDecrator : IDumbData
+{
+	protected IDumbData data;
+
+	public BaseDecrator(IDumbData data) => this.data = data;
+
+	public virtual int Id { get => data.Id; set => data.Id = value; }
+	public virtual string Name { get => data.Name; set => data.Name = value; }
+	public virtual string Description { get => data.Description; set => data.Description = value; }
+}
+
+public class InjectedFunctionality : BaseDecrator
+{
+	// supply original known object as parameter
+	// enables composability
+	public InjectedFunctionality(IDumbData data) : base(data) { }
+
+	public override string Name
+	{
+		get => data.Name;
+		set
+		{
+			data.Name = value
+			EmitEvent(value);
+		}
+	}
+
+	private void EmitEvent(string name)
+	{
+		// added functionality/responsiblity is not know to the outside, 
+		// in favour of ability to pick decoration at runtime
+	}
+}

decorator/funcational.linq

@@ -0,0 +1,35 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	Func<int, int, int> add = PrintResult(Add);
+	Func<int, int, int> addPrintSquare = Square(add);
+	Func<int, int, int> addSquarePrint = PrintResult(Square(Add));
+
+	add(5, 5);
+	addPrintSquare(5, 5).Dump("after");
+	addSquarePrint(5, 5);
+}
+
+public int Add(int a, int b) => a + b;
+
+public Func<int, int, int> PrintResult(Func<int, int, int> fn)
+{
+	return (int a, int b) =>
+	{
+		int result = fn(a, b);
+
+		result.Dump("inside");
+
+		return result;
+	};
+}
+
+public Func<int, int, int> Square(Func<int, int, int> fn)
+{
+	return (int a, int b) =>
+	{
+		int result = fn(a, b);
+		return result * result;
+	};
+}

decorator/simpler.linq

@@ -0,0 +1,59 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	var d = new Doer();
+	d.Something();
+	"---".Dump();
+	
+	var atd = new AnotherThing(d);
+	atd.Something();
+	"---".Dump();
+	
+	var iad = new InAddition(d);
+	iad.Something();
+	"---".Dump();
+	
+	var iaatd = new InAddition(atd);
+	iaatd.Something();
+	"---".Dump();
+	
+	var atiad = new AnotherThing(iad);
+	atiad.Something();
+}
+
+public interface IDoSomething
+{
+	void Something();
+}
+
+public class Doer : IDoSomething
+{
+	public void Something() => "Something".Dump();
+}
+
+public class AnotherThing : IDoSomething
+{
+	protected IDoSomething _doSomething;
+
+	public AnotherThing(IDoSomething doSomething) => _doSomething = doSomething;
+
+	public void Something()
+	{
+		_doSomething.Something();
+		"Another Thing".Dump();
+	}
+}
+
+public class InAddition : IDoSomething
+{
+	protected IDoSomething _doSomething;
+
+	public InAddition(IDoSomething doSomething) => _doSomething = doSomething;
+
+	public void Something()
+	{
+		_doSomething.Something();
+		"In Addition".Dump();
+	}
+}

proxy/protection.linq

@@ -0,0 +1,46 @@
+<Query Kind="Program" />
+
+void Main()
+{
+
+}
+
+public interface ISettings
+{
+	string GetConfig();
+}
+
+public class Settings : ISettings
+{
+	string _config;
+
+	public Settings(string config) => _config = config;
+
+	public string GetConfig() => _config;
+}
+
+public class ProtectedSettings : ISettings
+{
+	AuthService _auth;
+	Settings _config;
+
+	public ProtectedSettings(AuthService auth)
+	{
+		_auth = auth;
+		_config = new Settings("config");
+	}
+
+	public string GetConfig()
+	{
+		if (!_auth.Allowed)
+		{
+			throw new Exception("not allowed");
+		}
+		return _config.GetConfig();
+	}
+}
+
+public class AuthService
+{
+	public bool Allowed => false;
+}

proxy/remote.linq

@@ -0,0 +1,36 @@
+<Query Kind="Program" />
+
+void Main()
+{
+
+}
+
+public interface ISettings
+{
+	string GetConfig();
+}
+
+public class Settings : ISettings
+{
+	string _config;
+	
+	public Settings(string config) => _config = config;
+	
+	public string GetConfig() => _config;
+}
+
+public class RemoteSettings : ISettings
+{
+	Settings _config;
+	
+	public RemoteSettings(string address)
+	{
+		// fetch from appsettings/db/registry etc...
+		_config = new Settings("config");
+	}
+
+	public string GetConfig() {
+		
+		return "";
+	}
+}

proxy/the_fine_line.linq

@@ -0,0 +1,33 @@
+<Query Kind="Program" />
+
+void Main()
+{
+
+}
+
+public interface Abstraction { }
+
+public class Concretion : Abstraction { }
+
+public class ConcretionProxy : Abstraction
+{
+	// hide concretion, if we inject it we already exposed it
+	// compile time decision
+	Concretion concretion = new Concretion();
+
+	// simulate/hook/intercept/interupt communication with Concretion
+}
+
+public class CocretionDecorator : Abstraction
+{
+	Abstraction _abstraction;
+
+	// concretion is known
+	// runtime decsion
+	public CocretionDecorator(Abstraction abstraction)
+	{
+		_abstraction = abstraction;
+	}
+
+	// override concretion functionality
+}

proxy/virtual.linq

@@ -0,0 +1,42 @@
+<Query Kind="Program" />
+
+void Main()
+{
+	var a = new Lazy<string>(() => "Hello World".Dump("a"));
+	var b = a.Value;
+	var c = a.Value;
+}
+
+public interface ISettings
+{
+	string GetConfig();
+}
+
+public class Settings : ISettings
+{
+	string _config;
+	
+	public Settings(string config) => _config = config;
+	
+	public string GetConfig() => _config;
+}
+
+public class LazyRemoteSettings : ISettings
+{
+	Settings _config;
+
+	public LazyRemoteSettings(string address)
+	{
+		// prepare some http/db
+	}
+
+	public string GetConfig()
+	{
+		if (_config == null)
+		{
+			// fetch from appsettings/db/registry etc...
+			_config = new Settings("config");
+		}
+		return "";
+	}
+}