Keeping an updated model class and accessing it from multiple view controllers in Swift?

Question

I am making an app with swift and xcode. In it I have a model class with user's information in it. I want to display some of that information with one view controller, update/change that information in another, and keep all of the views up-to-date with whatever is in the model class.

I was told using a singleton could work but is not recommended. Is there a better, more accepted way of accessing the model class from multiple view controllers without a segue between them (I am using a tabBarViewController)?

Answer 1

If you want to go "pure" that is follow Apple Best practices where a View Controller is never hard-coded to a global model (more of a pain than is worth, practically, in my opinion):

1. Subclass UITabBarController to contain the model instance as a stored property (perhaps private(set) is the best access level here, but however you want to expose it safely to other classes -- PUBLICLY EXPOSED AS A PROTOCOL TYPE ONLY OF COURSE.)

2. Don't forget to set the identity class of your Storyboard Tab VC to this new subclass otherwise your sexy code will not run.

3. In your (hopefully base class to all child tab VCs) View Controller class, hook into didMoveToParentViewController(parent: UIViewController) . Gently downcast ( as? ) to the UITabBar subclass above, and extract the model, and copy the reference into your local stored property. It will happen exactly at the right time, just as you land into the soft arms of your parent VC.

Happiness!

Answer 2

You can try KVO mechanism. By which if you change a model variable's value that will reflect in another controller. For your reference https://www.appcoda.com/understanding-key-value-observing-coding/