Merge pull request #4 from AmdHamdani/master

Adding NullObject pattern

Author: beginor

NullObject/AbstractBook.cs

@@ -0,0 +1,7 @@
+using System;
+
+public abstract class AbstractCustomer {
+	protected string title;
+	
+	public abstract string GetTitle();
+}

NullObject/Book.cs

@@ -0,0 +1,12 @@
+using System;
+
+public class Book : AbstractCustomer {
+	
+	public Book (String title) {
+		this.title = title;
+	}
+	
+	public override string GetTitle() {
+		return title;
+	}
+}

NullObject/BookFactory.cs

@@ -0,0 +1,14 @@
+using System;
+
+public class BookFactory {
+	
+	public static string[] books = {"Book1", "Book2", "Book3" };
+	
+	public static AbstractCustomer GetBook(string title) {
+		for(int i = 0; i < books.Length; i++)
+			if(books[i] == title)
+				return new Book(title);
+		return new NullBook();
+	}
+	
+}

NullObject/Client.cs

@@ -0,0 +1,20 @@
+using System;
+
+public class NullPatternDemo {
+	
+	static void Main(string[] args) {
+		
+		AbstractCustomer c1 = BookFactory.GetBook("Book1");
+		AbstractCustomer c2 = BookFactory.GetBook("Book5");
+		AbstractCustomer c3 = BookFactory.GetBook("Book2");
+		AbstractCustomer c4 = BookFactory.GetBook("Book3");
+		AbstractCustomer c5 = BookFactory.GetBook("Book9");
+		
+		Console.WriteLine(c1.GetTitle());
+		Console.WriteLine(c2.GetTitle());
+		Console.WriteLine(c3.GetTitle());
+		Console.WriteLine(c4.GetTitle());
+		Console.WriteLine(c5.GetTitle());
+	}
+	
+}

NullObject/NullBook.cs

@@ -0,0 +1,9 @@
+using System;
+
+class NullBook : AbstractCustomer {
+	
+	public override string GetTitle() {
+		return "Not avaible in Customer Database";
+	}
+	
+}