An Xcode 9 project, written in Swift 4, demonstrating how to implement the observer design pattern.
In this repo and accompanying tutorial, I explain the observer design pattern, where one instance, the subject, notifies (many) other instances, the observers, of changes to the state of the subject. The instances participating in this broadcast type communication don't need to know about one another. This is a great example of loose coupling. The subject instance, usually a single critical resource, broadcasts notifications about a change in its state to many observer instances that depend on that resource. Interested observers must subscribe to get notifications.
Here's the app -- resulting from building this project in Xcode -- in action:
Xcode 9 project settings
To get this project running on the Simulator or a physical device (iPhone, iPad), go to the following locations in Xcode and make the suggested changes:
- Project Navigator -> [Project Name] -> Targets List -> TARGETS -> [Target Name] -> General -> Signing
- Tick the "Automatically manage signing" box
- Select a valid name from the "Team" dropdown
- Project Navigator -> [Project Name] -> Targets List -> TARGETS -> [Target Name] -> General -> Identity
- Change the "com.yourDomainNameHere" portion of the value in the "Bundle Identifier" text field to your real reverse domain name (i.e., "com.yourRealDomainName.Project-Name").