Add observer pattern

Update memento pattern examples class to have run as static method
Update behavioral patterns program.cs to maintain the order

BehavioralPatterns.sln

@@ -22,6 +22,8 @@ Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "MediatorPattern", "src\Medi
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "MememntoPattern", "src\MememntoPattern\MememntoPattern.xproj", "{1DE3FDD3-D025-49D8-BEF4-D5F0688F89E8}"
 EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "ObserverPattern", "src\ObserverPattern\ObserverPattern.xproj", "{D48DB558-0228-4ACE-88A8-A202E5C57849}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -52,6 +54,10 @@ Global
 		{1DE3FDD3-D025-49D8-BEF4-D5F0688F89E8}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{1DE3FDD3-D025-49D8-BEF4-D5F0688F89E8}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{1DE3FDD3-D025-49D8-BEF4-D5F0688F89E8}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D48DB558-0228-4ACE-88A8-A202E5C57849}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D48DB558-0228-4ACE-88A8-A202E5C57849}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D48DB558-0228-4ACE-88A8-A202E5C57849}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D48DB558-0228-4ACE-88A8-A202E5C57849}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -63,5 +69,6 @@ Global
 		{6F3B7F9A-4D9C-4506-A5F7-3FF5CF4376BD} = {3820200F-354C-41E6-8F34-B301F5D621C2}
 		{2A63BD0A-9D07-4755-9B16-5DDBEB075B80} = {3820200F-354C-41E6-8F34-B301F5D621C2}
 		{1DE3FDD3-D025-49D8-BEF4-D5F0688F89E8} = {3820200F-354C-41E6-8F34-B301F5D621C2}
+		{D48DB558-0228-4ACE-88A8-A202E5C57849} = {3820200F-354C-41E6-8F34-B301F5D621C2}
 	EndGlobalSection
 EndGlobal

src/BehavioralPatterns/Program.cs

@@ -4,6 +4,7 @@ using CommandPattern;
 using IteratorPattern;
 using MediatorPattern;
 using MememntoPattern;
+using ObserverPattern;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -17,10 +18,6 @@ namespace BehavioralPatterns
         public static void Main(string[] args)
         {           
 
-            MementoPatternExamples mementoPattern = new MementoPatternExamples();
-            mementoPattern.Run();
-
-            MediatorPatternExamples.Run();
             //Chain of responsibillity
             //This is usefull when you have a request and you don't know who should process it
             ChainOfResponsibillityExamples.Run();
@@ -35,8 +32,18 @@ namespace BehavioralPatterns
             Console.ReadKey();
 
             IteratorPatternExamples.Run();
+
             Console.ReadKey();
 
+            MediatorPatternExamples.Run();
+
+            Console.ReadKey();
+
+            MementoPatternExamples.Run();
+
+
+            ObserverPatternExamples.Run();
+            Console.ReadKey();
         }
     }
 }

src/BehavioralPatterns/project.json

@@ -16,7 +16,8 @@
     "Microsoft.NETCore.App": {
       "type": "platform",
       "version": "1.0.0-rc2-3002702"
-    }
+    },
+    "ObserverPattern": "1.0.0-*"
   },
 
   "frameworks": {

src/MememntoPattern/MementoPatternExamples.cs

@@ -7,16 +7,10 @@ using System.Threading.Tasks;
 
 namespace MememntoPattern
 {    
-    // This project can output the Class library as a NuGet Package.
-    // To enable this option, right-click on the project and select the Properties menu item. In the Build tab select "Produce outputs on build".
     public class MementoPatternExamples
-    {
-        public MementoPatternExamples()
     {
 
-        }
+        public static void Run()
-
-        public void Run()
         {
             Console.WriteLine(GetWhenToUse());
             Console.WriteLine(GetActors());
@@ -37,7 +31,7 @@ namespace MememntoPattern
             Console.WriteLine(GetPitfalls());
         }
 
-        string GetWhenToUse()
+        static string GetWhenToUse()
         {
             return @"When to use:
 When you need to be able to track the state of an object,or/and restore previous states as needed
@@ -48,14 +42,14 @@ Database transactions.
 
 
 
-        string GetAlternatives()
+        static string GetAlternatives()
         {
             return @"Alternatives:
 Command undo - when operations maybe undone
 Iterative Memento - Save the changes, instead of storing the entire state again like GIT";
         }
 
-        string GetActors()
+        static string GetActors()
         {
             return @"Actors:
 Originator: object that we want to save. It will create the actual memento.
@@ -63,7 +57,7 @@ Caretaker: keeps the mementos
 Memento: (Magic cookie) internal state of the object";
         }
 
-        string GetPitfalls()
+        static string GetPitfalls()
         {
             return @"
 Can be expensive

src/ObserverPattern/ObserverPattern.xproj

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+
+  <Import Project="$(VSToolsPath)\DotNet\Microsoft.DotNet.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>d48db558-0228-4ace-88a8-a202e5c57849</ProjectGuid>
+    <RootNamespace>ObserverPattern</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">.\obj</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">.\bin\</OutputPath>
+    <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DotNet\Microsoft.DotNet.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

src/ObserverPattern/ObserverPatternExamples.cs

@@ -0,0 +1,18 @@
+using ObserverPattern.Twits;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace ObserverPattern
+{
+    
+    public class ObserverPatternExamples
+    {
+        public static void Run()
+        {
+            ObservableTwitsExample obsTwits = new ObservableTwitsExample();
+            obsTwits.Run();
+        }
+    }
+}

src/ObserverPattern/Properties/AssemblyInfo.cs

@@ -0,0 +1,19 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("Hewlett-Packard Company")]
+[assembly: AssemblyProduct("ObserverPattern")]
+[assembly: AssemblyTrademark("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible
+// to COM components.  If you need to access a type in this assembly from
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("d48db558-0228-4ace-88a8-a202e5c57849")]

src/ObserverPattern/Twits/ObservableTwitsExample.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace ObserverPattern.Twits
+{
+    public class ObservableTwitsExample
+    {
+        public void Run()
+        {
+            TwitObservable observable = new TwitObservable();
+
+            TwitUser t100 = new TwitUser("t100");
+            TwitUser r2d2 = new TwitUser("r2d2");
+            
+            var t100Subscription = observable.Subscribe(t100);
+            var r2d2Subscription = observable.Subscribe(r2d2);
+
+            observable.AddTwit("El chupacapra");
+
+            t100Subscription.Dispose();
+
+            observable.AddTwit("Vamos vamos mi amor");
+
+            observable.ItsGoingHomeTime();
+
+            
+        }
+    }
+}

src/ObserverPattern/Twits/TwitObservable.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace ObserverPattern.Twits
+{
+    /// <summary>
+    /// Concrete observable
+    /// </summary>
+    public class TwitObservable : IObservable<string>
+    {
+        List<IObserver<string>> observers;
+        public TwitObservable()
+        {
+            observers = new List<IObserver<string>>();
+        }
+        public IDisposable Subscribe(IObserver<string> observer)
+        {
+            if (!observers.Contains(observer))
+                observers.Add(observer);
+
+            return new Unsubscriber(observers, observer);
+        }
+
+        public void AddTwit(string twit)
+        {
+            foreach (var observer in observers)
+            {
+                observer.OnNext(twit);
+            }
+        }   
+        
+        public void ItsGoingHomeTime()
+        {
+            foreach (var observer in observers)
+            {
+                observer.OnCompleted();
+            }
+        }     
+
+        private class Unsubscriber : IDisposable
+        {
+            private List<IObserver<string>> _observers;
+            private IObserver<string> _observer;
+
+            public Unsubscriber(List<IObserver<string>> observers, IObserver<string> observer)
+            {
+                _observers = observers;
+                _observer = observer;
+            }
+
+            public void Dispose()
+            {
+                if (!(_observer == null)) _observers.Remove(_observer);
+            }
+        }
+    }
+
+
+}

src/ObserverPattern/Twits/TwitUser.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace ObserverPattern.Twits
+{
+    /// <summary>
+    /// Concrete observer
+    /// </summary>
+    public class TwitUser : IObserver<string>
+    {
+        string name;
+        public TwitUser(string name)
+        {
+            this.name = name;
+        }
+        public void OnCompleted()
+        {
+            Console.WriteLine("{0} finished watching twitter", name);
+        }
+
+        public void OnError(Exception error)
+        {
+            Console.WriteLine("Error while watching twitter: {0}", error);
+        }
+
+        public void OnNext(string value)
+        {
+            Console.WriteLine("{0} just observed that something {1} was tweeted", name, value);
+        }
+    }
+}

src/ObserverPattern/project.json

@@ -0,0 +1,13 @@
+{
+  "version": "1.0.0-*",
+
+  "dependencies": {
+    "NETStandard.Library": "1.5.0-rc2-24027"
+  },
+
+  "frameworks": {
+    "netstandard1.5": {
+      "imports": "dnxcore50"
+    }
+  }
+}