best way to toggle done button on UITextField and UITextView (iPhone)

gistfile1.m

/*

set the UITextField's and UITextView's delegates to file owners!

put at .h file
*/

id activeField;

/*
put at .m file
*/

// -------------- Show/hide done button delegates --------------
- (void)textViewDidEndEditing:(UITextView *)textView
{
    activeField = nil;
}

- (void)textFieldDidEndEditing:(UITextField *)textField
{
	activeField = nil;
}

- (void)textViewDidBeginEditing:(UITextView *)textView
{
	activeField = textView;
	NSLog(@"activeField: (UITextView) %@", activeField);

	UIBarButtonItem *done = [[[UIBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Done", @"")
															  style:UIBarButtonItemStyleBordered
															 target:self
															 action:@selector(dismissKeyboard)] autorelease];

	self.navigationItem.rightBarButtonItem = done;
}

- (void)textFieldDidBeginEditing:(UITextField *)textField
{
	activeField = textField;
	NSLog(@"activeField: (UITextField) %@", activeField);
	
	UIBarButtonItem *done = [[[UIBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Done", @"")
															  style:UIBarButtonItemStyleBordered
															 target:self
															 action:@selector(dismissKeyboard)] autorelease];
	
	self.navigationItem.rightBarButtonItem = done;
}

- (void)dismissKeyboard
{
	NSLog(@"dismissKeyboard with active field: %@", activeField);

	[activeField resignFirstResponder];
	// remove done button from navigation
	self.navigationItem.rightBarButtonItem = nil;
}
// -------------- Show/hide done button delegates --------------