class ViewModel: ObservableObject {

    @Published var firstSwitch: Bool = false
    @Published var secondSwitch: Bool = false

    var isValid: AnyPublisher<Bool,Never> {
        return $firstSwitch
            .combineLatest($secondSwitch)
            .map { $0.0 && $0.1 }
            .eraseToAnyPublisher()
    }
    ...