A class written in Swift that simplifies how notification works in iOS.

SwiftyBus.swift

class SwiftyBus {
    
    private static let notificationQueue = DispatchQueue(label: "com.swiftybus.notification")
    
    struct Observer {
        let callback: Any
        let queue: DispatchQueue
    }
    
    static let shared = SwiftyBus()
    
    private var pools: [String: [String: Observer]] = [:]
    
    @discardableResult
    func register<T>(indexKey: String = UUID().uuidString, queue: DispatchQueue = notificationQueue, observer: @escaping (T) ->  Void) -> String {
        let key = "\(type(of: T.self))"
        var cPool = pools[key] ?? [:]
        cPool[indexKey] = Observer(callback: observer, queue: queue)
        pools[key] = cPool
        return indexKey
    }
    
    @discardableResult
    func unregister<T>(indexKey: String) -> ((T) -> Void)? {
        let key = "\(type(of: T.self))"
        guard var cPool = pools[key] else { return nil }
        let observer = cPool.removeValue(forKey: indexKey)
        pools[key] = cPool
        
        return observer?.callback as? (T) -> Void
    }
    
    func notify<T>(object: T) {
        let key = "\(type(of: T.self))"
        guard let cPool = pools[key] else { return }
        cPool.values.forEach { item in
            guard let observer = item.callback as? (T) -> Void else { return }
            item.queue.async {
                observer(object)
            }
        }
    }
}

Sample Usage

struct Person {
    let name: String
    let age: Int
}

class Publisher {
    init() {}
    func post(person: Person) {
        SwiftyBus.shared.notify(object: person)
    }
}

class Subscriber {
    let token: String

    init(tag: String) {
        token = SwiftyBus.shared.register { (p: Person) -> Void in
            print("SUBSCRIBER \(tag): A new person is coming, \(p.name) at \(p.age)")
        }
    }

    func unregister() {
        let _: ((Person) -> Void)? = SwiftyBus.shared.unregister(indexKey: token)
    }
}

let jin = Person(name: "Jin", age: 25)
let publisher = Publisher()
let google = Subscriber(tag: "Google")
let apple = Subscriber(tag: "Apple")

publisher.post(person: jin)

let sam = Person(name: "Sam", age: 46)
google.unregister()

publisher.post(person: sam)