NotificationCenter.Publisher VS PassThroughSubject - swift

Question

I have an object which I want to send throughout multiple listeners/subscribers, so I was checking out Combine and I saw 2 different kind of publishers, namely NotificationCenter.Publisher and PassThroughSubject. I am confused why anyone would use a NotificationCenter.Publisher over PassThroughSubject.
I came up with the code below, demonstrating both ways. To summarize:
NotificationCenter.Publisher needs to have a Notification.Name static property
Isn't really that typesafe (since I can post a different kind of object for the same Notification.Name/different publisher for the same Notification.Name)
Posting a new value needs to be done on NotificationCenter.default (not the publisher itself)
An explicit downcast to the used type in the map closure
In what scenarios someone will use NotificationCenter.Publisher over PassThroughSubject?
import UIKit
import Combine
let passThroughSubjectPublisher = PassthroughSubject<String, Never>()
let notificationCenterPublisher = NotificationCenter.default.publisher(for: .name).map { $0.object as! String }
extension Notification.Name {
static let name = Notification.Name(rawValue: "someName")
}
class PassThroughSubjectPublisherSubscriber {
init() {
passThroughSubjectPublisher.sink { (_) in
// Process
}
}
}
class NotificationCenterPublisherSubscriber {
init() {
notificationCenterPublisher.sink { (_) in
// Process
}
}
}
class PassThroughSubjectPublisherSinker {
init() {
passThroughSubjectPublisher.send("Henlo!")
}
}
class NotificationCenterPublisherSinker {
init() {
NotificationCenter.default.post(name: .name, object: "Henlo!")
}
}

Answer 1

If you have to use a 3rd party framework that uses NotificationCenter.

Answer 2

NotificationCenter can be thought of as a first generation message passing system, while Combine is second generation. It has runtime overhead and requires casting the objects you can store in Notifications. Personally I would never use NotificationCenter when building an iOS 13 framework, but you do need to use it to access a lot of iOS notifications that are only published there. Basically in my personal projects I’m going to treat it as read only unless absolutely necessary.