Cocoa NSPasteboard polling

AppDelegate.m

@implementation AppDelegate {
    NSInteger lastChangeCount;
    NSPasteboard *pasteboard;
}

- (void)applicationDidFinishLaunching:(NSNotification *)notification {
    pasteboard = [NSPasteboard generalPasteboard];
    [NSTimer scheduledTimerWithTimeInterval:0.25 target:self selector:@selector(checkPasteboard:) userInfo:nil repeats:YES];
}

- (void)checkPasteboard:(NSTimer *)timer {
    NSInteger currentChangeCount = [pasteboard changeCount];
    if (currentChangeCount == lastChangeCount)
        return;
    NSLog(@"Pasteboard changed: %@", [pasteboard types]);
    lastChangeCount = currentChangeCount;
}