swiftui - How to define a protocol to include a property with @Published property wrapper

Question

When using @Published property wrapper following current SwiftUI syntax, it seems very hard to define a protocol that includes a property with @Published, or I definitely need help :)

As I'm implementing dependency injection between a View and it's ViewModel, I need to define a ViewModelProtocol so to inject mock data to preview easily.

This is what I first tried,

protocol PersonViewModelProtocol {
    @Published var person: Person
}

I get "Property 'person' declared inside a protocol cannot have a wrapper".

Then I tried this,

protocol PersonViewModelProtocol {
    var $person: Published
}

Obviously didn't work because '$' is reserved.

I'm hoping a way to put a protocol between View and it's ViewModel and also leveraging the elegant @Published syntax. Thanks a lot.

Answer 1

You have to be explicit and describe all synthetized properties:

protocol WelcomeViewModel {
    var person: Person { get }
    var personPublished: Published<Person> { get }
    var personPublisher: Published<Person>.Publisher { get }
}

class ViewModel: ObservableObject {
    @Published var person: Person = Person()
    var personPublished: Published<Person> { _person }
    var personPublisher: Published<Person>.Publisher { $person }
}