NotificationCenter has long been a staple of iOS development, offering developers a flexible broadcast–subscribe mechanism. However, as Swift’s concurrency model has advanced, the traditional approach—using string-based identifiers and a userInfo dictionary—has revealed several pitfalls: thread-safety hazards, silent typos, and unsafe type casts. These issues often only surface at runtime.

To eliminate these pain points, Swift 6.2 introduces a brand-new, concurrency-safe notification protocols in Foundation: NotificationCenter.MainActorMessage and NotificationCenter.AsyncMessage. Leveraging Swift’s type system and concurrency isolation, it validates both posting and observing at compile time, completely eradicating common problems like “wrong thread” or “payload type mismatch.”