Which one of the two NSTextViews has been edited? doCommandBySelector is always returns the first one - objective-c

Question

I'm desperate to find the answer, so I opened TextLayoutDemo sample project from Apple. The point is that: I have two NSTextViews for column view. Everything works fine, text I enter is successfully laying out in those two text views via single layout manager:
NSLayoutManager *twoColumnLayoutManager = [[NSLayoutManager alloc] init];
NSTextContainer *firstColumnTextContainer = [[NSTextContainer alloc] init];
NSTextContainer *secondColumnTextContainer = [[NSTextContainer alloc] init];
NSTextView *firstColumnTextView = [[NSTextView alloc] initWithFrame:NSMakeRect(0, 0, 240, 360) textContainer:firstColumnTextContainer];
firstColumnTextView.delegate = self;
NSTextView *secondColumnTextView = [[NSTextView alloc] initWithFrame:NSMakeRect(240, 0, 240, 360) textContainer:secondColumnTextContainer];
secondColumnTextView.delegate = self;
[firstColumnTextContainer setContainerSize:NSMakeSize(240, 360)];
[secondColumnTextContainer setContainerSize:NSMakeSize(240, 360)];
[twoColumnLayoutManager addTextContainer:firstColumnTextContainer];
[twoColumnLayoutManager addTextContainer:secondColumnTextContainer];
[twoColumnLayoutManager replaceTextStorage:[firstTextView textStorage]];
[[secondWindow contentView] addSubview:firstColumnTextView];
[[secondWindow contentView] addSubview:secondColumnTextView];
But my goal is to get to know in which one text views the user edits a text. If it's the left one, I need to call one method, but if it's the right one, I want to call another method. And it seems impossible to recognize the correct text view, because delegate always get notified by the first text view.
- (BOOL) textView:(NSTextView *)textView doCommandBySelector:(SEL)commandSelector {
NSLog(#"edit: %#", textView);
return NO;
}
This method is always prints the first text view, even if I change text in the second one. And I see it's going according to docs, where Apple says there always will be just the first NSTextView in series.
But how can I solve my problem then?

Answer 1

Just tell me, if this solution is the one I am looking for. Because, in fact, it works just fine. The one thing I don't understand is why Cocoa text system is so tricky where it is not necessary?
- (void)textStorageDidProcessEditing:(NSNotification *)aNotification {
// that's the active text view
NSWindow *keyWindow = [[NSApplication sharedApplication] keyWindow];
NSTextView *activeTextView = (NSTextView *)[keyWindow firstResponder];
NSLog(#"%p", activeTextView);
}
UPDATE: this works only if user clicked the mouse button. Arrow keys do not update window's first responder:(