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Understanding SwiftUI Data Flow
A primer on some key protocols and property wrappers
I’ve seen many people having trouble architecting their apps in SwiftUI — because it’s a totally new paradigm and because it has very little official documentation. I want to use this article to share my use case of the various property wrappers exposed by SwiftUI, to help the data flow within your application.
Even if it’s a bit outdated (because SwiftUI already received a lot of refactors), I can’t recommend the 2019 WWDC session about SwiftUI data flow enough. It was thanks to this session that I first grasped the full power of SwiftUI and bootstrapped MovieSwiftUI.
You have to take a look at the SwiftUI data flow documentation from Apple, which is up to date and not bad at all. It somewhat lacks concrete examples, which is what I’ll try to provide in this article.
ObservableObject
ObservableObject is a protocol that’s part of the Combine framework. To use it you just have to add the protocol to your model class, then mark @Published any properties you want to be observed by SwiftUI within this model.
When to use it?
It’s a good protocol to use on your ViewModel, or your model directly if you don’t have or don’t need ViewModel. Basically, any object that needs to hold properties that you’ll directly use in your view should be marked/wrapped, in @Published, within an ObservableObject. You can think of it as the SwiftUI model…
