Completed class for my tutorial 'Fetching all your data from AWS AppSync'

fetch-all-data-appsync.swift

class OrderService {

    static let shared = OrderService()
    private var appSyncClient: AWSAppSyncClient?
    
    public var orders: [Order] = []
    
    private init() {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        appSyncClient = appDelegate.appSyncClient
    }
    
    func fetchOrders(nextToken: String?=nil, _ completion: @escaping (Swift.Result<Result, Error>) -> Void) {
        appSyncClient?.fetch(
            query: ListOrdersQuery(limit: 1000, nextToken: nextToken), cachePolicy: .fetchIgnoringCacheData
        ) { (result, error) in
            if let error = error {
                completion(.failure(error))
            } else {
                
                if let items = result?.data?.listOrders?.items {
                    for item in items {
                        self.orders.append(Order(
                            id: item?.id,
                            sku: item?.sku,
                            price: item?.price
                        ))
                    }
                }
                
                if let nextToken = result?.data?.listOrders?.nextToken {
                    self.fetchOrders(nextToken: nextToken) { result in
                        completion(result)
                    }
                } else {
                    completion(.success("Completed fetching!"))                }
            }
        }
    }
}