Question

Why doesn’t this code work:

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    [NSEvent addGlobalMonitorForEventsMatchingMask:(NSScrollWheelMask) handler:^(struct NSEvent *event){
        [scrollEvent:event];
    }];
}

- (void)scrollEvent:event {
    NSLog( @"scroll" );
}

It says “‘scrollEvent’ undeclared”.

I’m just learning objc and cocoa, so I assume this is just a simple error.

Answer 1

Your code appears to have some bugs in it. I’ve cleaned up some, please see below.

- (void) applicationDidFinishLaunching:(NSNotification *) aNotification { 
    [NSEvent addGlobalMonitorForEventsMatchingMask: NSScrollWheelMask handler:^(NSEvent *event){ 
        [self scrollEvent: event]; 
    }]; 
} 

- (void) scrollEvent: (NSEvent *) event { 
    NSLog( @"scroll" ); 
}

To summarize:

• Your argument to the block should have been an NSEvent *, not a
  struct NSEvent *.
• Your invocation of scrollEvent needed to be sent to self.
• Your implementation of scrollEvent had an incorrect signature.

Hope that helps and good luck with the program.