7.3. Defining the names (identifiers) of the Notifications in a Better Way

In real life, the Notification Center is used very frequently, especially when we fetch data from the internet and wait for data to update. Oftentimes, it's pretty common to create tens of observers in a single app. So, just writing the names/identifiers of the notifications, as we did before, is not a good way of dealing with it. If the names do not match on both sides, notifications won't work. So, keeping the names in a separate class as static variables is better.

So, let's create a new Swift file (not a Cocoa touch class) called NotificationNames.swift.

Write the following code inside it:

//
//  NotificationNames.swift
//  App7
//
//  Created by Sakib Miazi on 5/22/23.
//

import Foundation
extension Notification.Name{
    static let textFromScondScreen = Notification.Name("textFromSecondScreen")
}

Here we are extending Notification.Name class, and defining new static names inside it. We used only one observer with the identity/name "textFromSecondScreen." textFromSecondScreen static constant is holding that identifier. So, now we will update the addObserver() and post() methods as follows:

addObserver() method:

Previously we had:

//MARK: observing text if it is updated in NotificationCenter...
notificationCenter.addObserver(
    self, selector: #selector(notificationReceivedForTextChanged(notification:)),
    name: Notification.Name("textFromSecondScreen"),
    object: nil)

We can now write:

//MARK: observing text if it is updated in NotificationCenter...
notificationCenter.addObserver(
    self, selector: #selector(notificationReceivedForTextChanged(notification:)),
    name: .textFromScondScreen,
    object: nil)

post() method:

Previously we had:

//MARK: posting text to NotificationCenter...
notificationCenter.post(
    name: Notification.Name("textFromSecondScreen"),
    object: text)

Now we can write:

//MARK: posting text to NotificationCenter...
notificationCenter.post(
    name: .textFromScondScreen,
    object: text)

This way, we can easily store multiple identifiers/names without worrying about fogetting and mismatching them.