macOS Queuing NSAlerts

[gwelmarten]

Hi
I'm running some code that can trigger multiple NSAlerts to be shown to a user in one go. I'm wrote:

            [pleaseLeaveReview beginSheetModalForWindow:window modalDelegate:self didEndSelector:@selector(someMethodDidEnd:returnCode:contextInfo:) contextInfo:nil];

to show the alerts that slide out from the top of the application.
Problem is, if I call one alert followed by another only the first one is shown - the next method is shown afterwards. When I've done this in iOS, they queue after each other automatically.
Is there a simple method I can use, or an if command to detect if an NSAlert is currently being shown?
Or should I use boolean values to detect if a message is being shown and set a NSTimer to re-call the message method if a message is already being shown.

Thanks,

Sam