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Working With NotificationCenter in iOS
How to broadcast messages in iOS and not put off Bob
There are multiple ways to communicate between components in the iOS world. You can pass parameters by constructor, segue, delegate pattern that is commonly used, or to choose NotificationCenter.
All these methods have a 1 on 1 relationship with exception of NotificationCenter, it is 1 to many. NotificationCenter is a really good tool to communicate between classes and structures, if it is used properly.
This article will explain how to:
- Observe simple Notification Posted by OS
- Observe Custom Notification created by us
- Observe Custom Notification what contains some Data
- How to avoid potential issues and crashes
Basics
On a high level it is broadcasting messages. The listeners / observer can receive these messages and do some actions or process them if they carry some information.
Imagine it, as when you subscribe to receive some newspaper, example from Better Programming.
Your 🐶 dog 🐾 will watch the mailbox for newspaper that is the Observer part.
When Better Programming sends out the newspaper, that is the Post part. Then you will receive from the Postman the newspaper in the mailbox.
But your neighbour, friend also could subscribe and receive it.
If you leave your address, and let’s say Bob moves in. And if you don’t remove the subscription, a new newspaper will still arrive. This is the Remove Observer part, you must remove yourself from the list who will be visited by the Postman.
Bob is a non technical person, who wants to understand everything. Bob maybe don’t understand the newspaper content and this will make him crazy. This is the possible crash part what will be explained latter.
The picture above represents the case where two ViewControllers and Service (green) subscribe and observe for the message, the…
