Swift Enum Values With Generics

Question

I wanted to make a parent view model that contains some basic stuff that I want all my view models to have in SwiftUI. I'm trying to make the parent view model have a generic variables so I can inherit ParentViewModel in any view model I make with the custom type.

This is what I've tried and got a Cannot find type 'T' in scope error on the loaded case. Not really sure how I can make that generic, any insight here?

class ParentViewModel: ObservableObject {
    enum Status {
        case loading
        case loaded(T)
        case error(Error)
    }
    
    @Published var status: Status = .loading
}

class ChildViewModel: ParentViewModel {
    
    init() {
        self.status = .loading
    }
    
    init(object: SomeObject) {
        self.status = .loaded(object)
    }
}

jnpdx · Accepted Answer · 2022-10-05 13:52:05Z

2

When you use a generic, you have to declare it in <>, which is missing in your example.

Here's a modified version that works:

class SomeObject { }

class ParentViewModel<T>: ObservableObject { // Declare T
    enum Status {
        case loading
        case loaded(T)
        case error(Error)
    }
    
    @Published var status: Status = .loading
}

class ChildViewModel: ParentViewModel<SomeObject> { // Specify that ParentViewModel will use SomeObject as T
    
    override init() {
        self.status = .loading
    }
    
    init(object: SomeObject) {
        self.status = .loaded(object)
    }
}

edited Oct 5, 2022 at 13:52

answered Oct 5, 2022 at 4:26

jnpdx

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