MacRuby NSBeginAlertSheet call gives unknown: [BUG] unknown Objective-C immediate: 0x1 (nil)

Question

As a MacRuby beginner I am working through this tutorial, and want to add a drop-down sheet to warn when the user tries to delete an entry from the app.

Following the code here, which in Obj-C is

- (IBAction)deleteRecord:(id)sender 
{
  NSString *title = @"Warning!";
  NSString *defaultButton = @"Delete";
  NSString *alternateButton = @"Don't Delete";
  NSString *otherButton = nil;
  NSString *message = @"Are you sure you want to delete the selected record(s)?";

  if ( [tableView numberOfSelectedRows] == 0 )
    return;

  NSBeep();
  NSBeginAlertSheet(title, defaultButton, alternateButton, otherButton, mainWindow, self, @selector(sheetDidEnd:returnCode:contextInfo:), nil, nil, message);
}

I have in MacRuby:

def removeFriend(sender)
  return if @friendsTableView.numberOfSelectedRows == 0
  title = 'Warning!'
  defaultButton = 'Delete'
  alternateButton = 'Don\'t Delete'
  otherButton = nil
  s = @friendsTableView.numberOfSelectedRows > 1 ? 's' : ''
  message = "Are you sure you want to delete the selected record#{s}?"
  NSBeginAlertSheet(title, defaultButton, alternateButton, otherButton, @mainWindow, self, :'alertDidEnd:returnCode:contextInfo:', nil, nil, message)
end

and for alertDidEnd:returnCode:contextInfo:

def alertDidEnd(sheet, returnCode:rCode, contextInfo:cInfo)
  <array handling code>
end

When this runs I get a drop-down sheet when the button linked to removeFriend is clicked, but then if I click "Delete" my app crashes with the following error:

unknown: [BUG] unknown Objective-C immediate: 0x1 (nil)

MacRuby 0.12 (ruby 1.9.2) [universal-darwin10.0, x86_64]

(lldb) 

Am I doing something wrong with the way the didAlertEnd method is implemented, or is this actually a bug?

Answer 1

Apparently a MacRuby bug: http://www.macruby.org/trac/ticket/1368