This abstraction contains either a success data of generic type `T` or an error of type `ErrorCode` as its result.

DataResult.swift

enum ErrorCode: Equatable, Error {
    case unknown

    // Top level server error
    case serverIssue

    // Network
    case noNetworkConnection
}

enum DataResult<T> {
    case success(value: T)
    case error(ErrorCode)

    var value: T? {
        switch self {
        case .success(value: let value):
            return value

        case .error:
            return nil
        }
    }

    var error: ErrorCode? {
        switch self {
        case .success:
            return nil

        case let .error(error):
            return error
        }
    }
}

extension DataResult: Equatable where T: Equatable {}