multiple BE calls for fetching data

multiple_fetching.swift

class ViewModel: ObservableObject {
    var bag = Set<AnyCancellable>()
    var t = "hellow"
    init() {
        let mainPublisher = [3, 2, 1].publisher
        mainPublisher.flatMap({ value in
            printit(value).map { calcualted in
                return (value, calcualted)
            }
        })
        .collect()
        .map({ result in
            print(result)
            return result
        })
        .sink(receiveValue: { _ in

        })
        .store(in: &bag)

    }
}

func printit(_ value: Int) -> Future<Int, Never> {
    return Future { promise in
        DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(value)) {
            print("printit -> \(value)")
            promise(.success(value * 2))
        }
    }
}