From 945b313529fe92a45a5145ac4acfef82f6a89a12 Mon Sep 17 00:00:00 2001
From: Daniel Langbein <daniel@systemli.org>
Date: Sat, 7 Dec 2024 13:11:42 +0100
Subject: [PATCH] wip

---
 ueb07_news_example_b/src/client/Client.java   | 19 ++++++++--
 .../src/model/NewsCollection.java             | 38 ++++++++++++++-----
 ueb07_news_example_b/src/model/NewsItem.java  |  8 +++-
 3 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/ueb07_news_example_b/src/client/Client.java b/ueb07_news_example_b/src/client/Client.java
index 94f2afd4..678aee2e 100644
--- a/ueb07_news_example_b/src/client/Client.java
+++ b/ueb07_news_example_b/src/client/Client.java
@@ -4,10 +4,18 @@ import model.Article;
 import model.Image;
 import model.NewsCollection;
 
-public class Client {
-	
-	public static void main(String[] args) {
+import java.util.Observable;
+import java.util.Observer;
+
+public class Client implements Observer {
+	public static void main(String[] args)  {
+		Client client = new Client();
+		client.run();
+	}
+
+	private void run() {
 		NewsCollection masterCollection = new NewsCollection("Daily news");
+		masterCollection.addObserver(this);
 
 		Article changedArticle = new Article("Harder, Better, Faster, Stronger. Doping controls loosened","ups");
 
@@ -28,4 +36,9 @@ public class Client {
 		changedArticle.setTitle("Harder, Better, Faster, Stronger? Doping controls loosened");
 		masterCollection.addItem(new Image("A tasty cat", 640, 480, "alf"));
 	}
+
+	@Override
+	public void update(Observable o, Object arg) {
+		System.out.println("### UPDATE ###\n" + arg + "\n");
+	}
 }
diff --git a/ueb07_news_example_b/src/model/NewsCollection.java b/ueb07_news_example_b/src/model/NewsCollection.java
index eab02042..341fb81d 100644
--- a/ueb07_news_example_b/src/model/NewsCollection.java
+++ b/ueb07_news_example_b/src/model/NewsCollection.java
@@ -1,24 +1,43 @@
 package model;
 
-import java.util.LinkedList;
-import java.util.List;
+import java.util.*;
 
 public class NewsCollection extends NewsItem {
-	
+
 	private List<NewsItem> newsItems = new LinkedList<NewsItem>();
-			
+
+	// We use a set to avoid duplicates.
+	Set<Observer> observers = new HashSet<>();
+
 	public NewsCollection(String topic) {
 		this.title = topic;
 	}
-	
-	/**
+
+    @Override
+	public void addObserver(Observer o) {
+		super.addObserver(o);
+        newsItems.forEach(item -> item.addObserver(o));
+
+        // Remember for later.
+		observers.add(o);
+	}
+
+    @Override
+    public void deleteObserver(Observer o){
+        super.deleteObserver(o);
+        newsItems.forEach(item -> item.deleteObserver(o));
+
+        observers.remove(o);
+    }
+
+    /**
 	 * Get the list of items stored in this collection.
 	 * @return items stored in this collection
 	 */
 	public List<NewsItem> getNewsItems() {
 		return newsItems;
 	}
-	
+
 	/**
 	 * Store another item to this collection.
 	 * @param item
@@ -26,9 +45,10 @@ public class NewsCollection extends NewsItem {
 	 */
 	public NewsCollection addItem(NewsItem item) {
 		newsItems.add(item);
+        observers.forEach(item::addObserver);
 		return this;
 	}
-	
+
 	/**
 	 * Print a list showing information about all directly or transitively
 	 * referenced items in the given collection.
@@ -54,5 +74,5 @@ public class NewsCollection extends NewsItem {
 			builder.append("\n");
 		}
 		return builder.toString();
-	}	
+	}
 }
diff --git a/ueb07_news_example_b/src/model/NewsItem.java b/ueb07_news_example_b/src/model/NewsItem.java
index e7b7a86a..3aa3e87e 100644
--- a/ueb07_news_example_b/src/model/NewsItem.java
+++ b/ueb07_news_example_b/src/model/NewsItem.java
@@ -1,7 +1,8 @@
 package model;
 
-public abstract class NewsItem {
+import java.util.Observable;
 
+public abstract class NewsItem extends Observable {
 	protected String title;
 
 	public NewsItem() {
@@ -17,6 +18,11 @@ public abstract class NewsItem {
 	}
 	
 	public void setTitle(String newTitle) {
+		if(title.equals(newTitle)) return;
+
+		setChanged();
+		notifyObservers("➖ " + title + "\n➕ " + newTitle);
+
 		title = newTitle;
 	}