快速完成处理程序 4.

Question

我有一个问题，我试图解决与使用完成处理程序有关的问题。我的iOS程序中有3层，ViewController->Service->Networking。我需要通过视图控制器的 API 调用加载一些数据。

我在 ViewController 中定义了函数(completionHandlers)，这些函数应在数据请求完成后执行，并且在仅存在两层时实现完成处理程序时很舒服，但在以下情况下感到困惑：

仪表板视图控制器.swift

import UIKit
@IBDesignable class DashboardViewController: UIViewController {
@IBOutlet weak var stepCountController: ExpandedCardView!
var articles:[Article]?
let requestHandler = RequestHandler()
let dashboardService = DashboardService()
override func viewDidLoad() {
super.viewDidLoad()
dashboardService.getDashboardData(completionHandler: getDashboardDataCompletionHandler)
}
func getDashboardDataCompletionHandler(withData: DashboardDataRequest) {
print(withData)
}
} 

仪表板服务.swift

import Foundation
class DashboardService: GeneralService {
var requestHandler: DashboardRequestHandler
override init() {
requestHandler = DashboardRequestHandler()
super.init()
}
//this function should execute requestHandler.requestDashboardData(), and then execute convertDashboardData() with the result of previous get request
func getDashboardData(completionHandler: @escaping (DashboardDataRequest) -> Void) {
//on network call return
guard let url = URL(string: apiResourceList?.value(forKey: "GetDashboard") as! String) else { return }
requestHandler.requestDashboardData(url: url, completionHandler: convertDashboardData(completionHandler: completionHandler))
}
func convertDashboardData(completionHandler: (DashboardDataRequest) -> Void) {
//convert object to format acceptable by view
}
}

DashboardRequestHandler.swift

import Foundation
class DashboardRequestHandler: RequestHandler {
var dataTask: URLSessionDataTask?
func requestDashboardData(url: URL, completionHandler: @escaping (DashboardDataRequest) -> Void) {
dataTask?.cancel()
defaultSession.dataTask(with: url, completionHandler: {(data, response, error) in
if error != nil {
print(error!.localizedDescription)
}
guard let data = data else {
return
}
do {
let decodedJson = try JSONDecoder().decode(DashboardDataRequest.self, from: data)
completionHandler(decodedJson)
} catch let jsonError {
print(jsonError)
}
}).resume()
}
}

如果您查看DashboardService.swift中的评论，我的问题很明显。我将完成处理程序从 ViewController 传递到服务，服务有自己的完成处理程序，它传递给 RequestHandler，其中视图控制器完成处理程序 (getDashboardDataCompletionHandler) 应在服务完成处理程序(转换仪表板数据())之后执行

请帮助我澄清如何实现这一点。我是否通过尝试链接这样的完成处理程序而犯了设计错误，或者我错过了一些明显的东西。

谢谢

--编辑-- 我的请求处理程序实现如下所示：

import Foundation
class RequestHandler {
//    let defaultSession = URLSession(configuration: .default)
var defaultSession: URLSession!
init() {
guard let path = Bundle.main.path(forResource: "Api", ofType: "plist") else {
print("Api.plist not found")
return
}
let apiResourceList = NSDictionary(contentsOfFile: path)
let config = URLSessionConfiguration.default
if let authToken = apiResourceList?.value(forKey: "AuthToken") {
config.httpAdditionalHeaders = ["Authorization": authToken]
}
defaultSession = URLSession(configuration: config)
}
}

Answer 1

在这种情况下使用委派更清楚，例如这样：

protocol DashboardServiceDelegate {
func didLoaded(_ viewModel: DashboardViewModel)
}
class DashboardViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
dashboardService.delegate = self
dashboardService.getDashboardData()
}
}
extension DashboardViewController: DashboardServiceDelegate {
func didLoaded(_ viewModel: DashboardViewModel) {
///
}
}

protocol DashboardRequestHandlerDelegate() {
func didLoaded(request: DashboardDataRequest)
}
class DashboardService: GeneralService {
private lazy var requestHandler: DashboardRequestHandler = { reqHandler in
reqHandler.delegate = self
return reqHandler
}(DashboardRequestHandler())
func getDashboardData() {
guard let url = ...
requestHandler.requestDashboardData(url: url)
}
}
extension DashboardService: DashboardRequestHandlerDelegate {
func didLoaded(request: DashboardDataRequest) {
let viewModel = convert(request)
delegate.didLoaded(viewModel)
}
}