From 4266447d1b3757ac6707c2617cb3e4b8c63aaa60 Mon Sep 17 00:00:00 2001
From: Arslaan Pathan <arslaan@arslaancodes.com>
Date: Fri, 2 Oct 2026 10:33:02 +1300
Subject: predicates/filtering and observers/KVO

---
 main.m | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

(limited to 'main.m')

diff --git a/main.m b/main.m
index 1839123..ef6c88f 100644
--- a/main.m
+++ b/main.m
@@ -102,6 +102,19 @@ static int playerCount = 0;
 
 @end
 
+@interface PlayerObserver : NSObject 
+@end
+
+@implementation PlayerObserver
+
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void*)context {
+	 NSLog(@"PlayerObserver: %@ changed!", keyPath);
+	 NSLog(@"Old: %@", [change objectForKey:NSKeyValueChangeOldKey]);
+	 NSLog(@"New: %@", [change objectForKey:NSKeyValueChangeNewKey]);
+}
+
+@end
+
 int main(void) {
 	@autoreleasepool {
 		Hello *hello = [Hello new];
@@ -139,8 +152,32 @@ int main(void) {
 
 		NSLog(@"%@", people);
 
+		NSArray *players = @[
+			@{@"name": @"French Hacker", @"score": @538},
+			@{@"name": @"Arslaan", @"score": @53827},
+			@{@"name": @"John Hackclub", @"score": @120}
+		];
+
+		NSPredicate *highScore = [NSPredicate predicateWithFormat:@"score > 300"];
+
+		NSArray *filtered = [players filteredArrayUsingPredicate:highScore];
+
+		NSLog(@"All players: %@", players);
+		NSLog(@"High scorers (score > 300): %@", filtered);
+
+		Player *player3 = [Player new];
+		PlayerObserver *observer = [PlayerObserver new];
+
+		[player3 addObserver:observer forKeyPath:@"name" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:NULL];
+		[player3 setName:@"Arslaan"];
+		[player3 setName:@"Arslaan Pathan"];
+
+		[player3 removeObserver:observer forKeyPath:@"name" context:NULL];
+
 		[player release];
 		[player2 release];
+		[observer release];
+		[player3 release];
 		[hello release];
 		[ehello release];
 		[dehello release];
-- 
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