提问人:Swift 提问时间:11/16/2023 更新时间:11/16/2023 访问量:41
MVVM 模式服务调用响应未出现在 swift 的 Viewcontroller 中
MVVM pattern service call response not coming in Viewcontroller in swift
问:
我正在使用MVVM模式进行服务调用
代码:在ViewController中,调用和响应也来了,但为什么为零?postGenericCallVM
print("testing viewmodel data in viewcontroller \(String(describing: postVM.postDataVM?.postCount))")
我哪里错了?
struct RequestObject {
var params: [String: Any]? = nil
var method: HTTPMethod
var urlPath: String
var isTokenNeeded: Bool
var isLoaderNeed: Bool = false
var isErrorNeed: Bool = false
var vc: UIViewController?
}
class APINetworkManager2: NSObject {
static let sharedInstance = APINetworkManager2()
fileprivate override init() {
super.init()
}
func serviceCall<T: Decodable>(requestObject: RequestObject, completion: @escaping (Result<APIResponse<T>, Error>) -> Void) {
guard let url = URL(string: requestObject.urlPath) else {
return
}
var urlRequest = URLRequest(url: url)
if requestObject.isTokenNeeded {
let token = "Bearer token" // Replace with your actual token
urlRequest.setValue(token, forHTTPHeaderField: "Authorization")
}
urlRequest.httpMethod = requestObject.method.rawValue
if let params = requestObject.params {
let paramsReq: [String: Any] = ["jsonrpc": "2.0", "params": params]
do {
urlRequest.httpBody = try JSONSerialization.data(withJSONObject: paramsReq)
} catch {
completion(.failure(error))
return
}
}
let task = URLSession.shared.dataTask(with: urlRequest) { data, _, error in
if let data, let string = String(data: data, encoding: .utf8) {
print("debug check \(string)")
}
do {
let response = try JSONDecoder().decode(APIResponse<T>.self, from: data!)
DispatchQueue.main.async {
completion(.success(response))
}
} catch {
DispatchQueue.main.async {
completion(.failure(error))
}
}
}
task.resume()
}
}
这是我的 VIewmodel 代码,在这里打印 o/p 结果视图模型:模型数据即将到来
class PostViewModel {
var postDataVM: PostGenResult?
func postGenericCallVM(){
let param = ["page_no" : "1"] as? [String:Any]
let requestObject = RequestObject(
params: param,
method: .post,
urlPath: "https://hsfjkhskdn",
isTokenNeeded: true,
isLoaderNeed: true,
isErrorNeed: true
)
APINetworkManager2.sharedInstance.serviceCall(requestObject: requestObject) { (result: Result<APIResponse<PostGenResult>, Error>) in
switch result {
case .success(let response):
self.postDataVM = response.result as? PostGenResult
print("result view model: \(self.postDataVM)")
case .failure(let error):
print("Error decoding JSON: \(error)")
}
}
}
}
O/P:在ViewController中成功获取响应
结果视图模型:可选(PracticeCode.PostGenResult(pageCount: 1, perPage: 10, postCount: 5, userReminder: [PracticeCode.UserReminder(id: 17, receiverID: 7, type: “Subscription”, message: “Your Subscription is due in 2
这是我的ViewController代码: 这里
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
postVM.postGenericCallVM()
print("testing viewmodel data in viewcontroller \(postVM.postDataVM?.postCount)")
}
}
服务呼叫正在呼叫和响应即将到来,但给出零testing viewmodel data in viewcontroller
在 ViewController 中测试 ViewModel 数据:NIL
答:
这是真的,因为您正在请求一个任务,并且需要一些时间进行回调。async
postVM.postGenericCallVM()
//Will execute on background thread
APINetworkManager2.sharedInstance.serviceCall
另一方面,这些代码将同步执行。有关更多详细信息,您可以在此处放置日志。
print("Requesting")
postVM.postGenericCallVM()
print("testing viewmodel data in viewcontroller \(postVM.postDataVM?.postCount)")
然后你会看到打印顺序应该是:
Requesting
testing viewmodel data in viewcontroller \(postVM.postDataVM?.postCount)
result view model: \(self.postDataVM)
如何处理?方法1,在函数中添加@escaping补全。postGenericCallVM
func postGenericCallVM(completion: @escaping (() -> Void)) {
...
switch result {
...
}
completion()
}
postVM.postGenericCallVM { [weak self] in
//TODO: Re-check postVM.postDataVM here
}
方法二、使用async await
func postGenericCallVM() async {
await withCheckedContinuation { continuetion in
...
APINetworkManager2.sharedInstance.serviceCall {
...
continuetion.resume(returning: ())
}
}
}
Task {
await postVM.postGenericCallVM()
print("\(postVM.postDataVM)")
}
评论
postVM.postGenericCallVM()
是异步调用,之后的 print 语句会立即执行,因此在 print 语句中它将是 nil。您可以转换为支持 async/await,或者使用基于闭包的回调,甚至使用基于 combine 的订阅者/发布者来了解 API 调用何时完成,以便随后可以执行 print 语句。postGenericCallVM()