Cocoa: Return to previous active application?

is there a way to capture application that was previously active, before my application was brought to front by user?

I've tried to this in applicationWillBecomeActive: delegate method, but my application is alread开发者_如何学Pythony mark as active.

Thanks.

Register for the NSWorkspaceDidDeactivateApplicationNotification notification in NSWorkspace. This will give you an NSRunningApplication instance of what was deactivated.