NotificationSmuggler

A Swift 6 package for type-safe notification handling with strongly-typed values with strict concurrency, using async/await or Combine publishers.

Never touch a userInfo dictionary again for your own notifications.

Overview

NotificationSmuggler makes it easy to embed strongly-typed values in Notifications and extract them on the receiving end. It "smuggles" your contraband payload through the userInfo dictionary while providing a clean, type-safe API.

Each conforming type gets its own unique notification name and userInfo key, automatically generated from the type name. There are convenience methods for posting and observing your contraband. Structs are recommended because you may want these to be Sendable, and inheritance isn't supported so hierarchies may pose pitfalls if you try to get fancy.

Getting Started

Define your contraband

Create a type that conforms to the Smuggled protocol:

struct AccountAuthenticated: Smuggled, Sendable {
    let accountID: String
    let timestamp: Date
}

Post Notifications

Use the convenience method to post directly:

NotificationCenter.default.smuggle(AccountAuthenticatedNotification(
    accountID: "abc123", 
    timestamp: .now
))

Or create a notification first if that's more convenient:

let notification = Notification.smuggle(AccountAuthenticatedNotification(
    accountID: "abc123", 
    timestamp: .now
))
NotificationCenter.default.post(notification)

Observe Notifications

With async/await (recommended for Sendable types):

Task {
    for await authenticated in NotificationCenter.default.notifications(for: AccountAuthenticatedNotification.self) {
        print("Account \(authenticated.accountID) authenticated at \(authenticated.timestamp)")
    }
}

With Combine:

NotificationCenter.default.publisher(for: AccountAuthenticatedNotification.self)
    .sink { authenticated in
        print("Account \(authenticated.accountID) authenticated")
    }
    .store(in: &cancellables)

Object-Specific Observation

Filter notifications by sender object:

let document = AwesomeDocument()

// Only receive notifications from this specific document
for await saved in NotificationCenter.default.notifications(for: DocumentSavedNotification.self, object: document) {
    print("Document saved: \(saved.filename)")
}

Topics

Essential Types

Smuggled

Notification Creation

Foundation/Notification/smuggle(_:object:)
Foundation/NotificationCenter/smuggle(_:object:)

Notification Observation

Foundation/NotificationCenter/notifications(for:object:)
Foundation/NotificationCenter/publisher(for:object:)

Extracting Values

Foundation/Notification/smuggled()

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