[英]How to successfully implement async and await in Swift, and whats the best method to use
基本上我正在尝试创建一个基本的登录页面,它将有一个 ContentView,它有一个在按下登录按钮时调用的方法。 将发生的情况是将用户名和密码发送到 NetworkManager class,它将评估 api,如果密码和用户名正确,它将返回 true,否则返回 false,这将更改 @Published 变量的真假。 在 ContentView 中观察到该特定变量以检查尝试登录是否成功。
我还有几个用于解码和编码的类。
现在我的问题是在我调用 NetworkManager 来检查 api 之后,我有一个条件来检查用户是否成功登录,但是因为网络调用返回的速度不够快,所以它总是返回 false,我该怎么做条件等待网络调用在继续之前返回。
在 java/C# 中,我只会使用 Async/Await,但对 swift 来说是新手,我尝试了几种不同的方法,但无法让它工作。 任何帮助,将不胜感激。 下面是我创建的三个 swift 文件、ContentView、NetworkManager class 以及用于构造发送和返回 json 数据的类。 由于显而易见的原因,我还更改了 api 的地址。 谢谢
内容视图
import SwiftUI
struct ContentView: View {
@ObservedObject var networkManager = NetworkManager()
let dispatchGroup = DispatchGroup()
let dispatchQueue = DispatchQueue(label: "My Queue")
@State private var usernameInput = ""
@State private var passwordInput = ""
@State private var returnType = ""
//private var returnType = ""
var body: some View {
VStack{
Text(networkManager.usernamesAndPass)
TextField("Enter Username", text: $usernameInput)
TextField("Pasword", text: $passwordInput)
Button(action: {
self.AttempLogin()
})
{
Text("Login")
}
}
}
func AttempLogin(){
dispatchQueue.async(group: dispatchGroup) {
self.networkManager.loginFunction(username: self.usernameInput, password: self.passwordInput)
}
dispatchQueue.async(group: dispatchGroup) {
if(self.networkManager.loggedIn){
print("You're now logged on")
}
else{
print("You aren't logged in")
}
}
dispatchGroup.wait()
print("Final")
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
网络管理器
import Foundation
class NetworkManager: ObservableObject {
@Published var loggedIn = Bool()
func loginFunction(username: String, password: String) {
let url = URL(string: "https://example.com.au/TestPHP/users/login")
let loginDetails = People(user_email: username, user_password: password)
//CHeck to see if the guard encoding works
let jsonData = try? JSONEncoder().encode(loginDetails)
var request = URLRequest(url: url!)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")//the JSON request
request.setValue("application/json", forHTTPHeaderField: "Accept") // the response expected to be in JSON format
request.httpBody = jsonData
let task = URLSession.shared.dataTask(with: request) { data, response, error in
if let error = error {
print("Error took place \(error)")
return
}
guard let data = data else {return}
do {
let getResponse = try JSONDecoder().decode(Response.self, from: data)
DispatchQueue.main.async {
self.loggedIn = getResponse.status
}
} catch let error {
print("Error: Trying to convert JSON data to string")
print(error)
return
}
}
task.resume()
}
}
用户类
class Response: Codable {
var status: Bool
var message: String
}
class People: Codable {
var user_emailaddress: String = String()
var user_password: String = String()
var status: String = String()
var logedIn: Bool = Bool()
var messaage: String = String()
init(user_email: String, user_password: String){
self.user_emailaddress = user_email
self.user_password = user_password
}
}
感谢任何人可以提供的任何帮助,任何真正擅长解释这一点的 tuts 都会很棒,正如我之前所说,我是 Swift 的新手,所以尽可能多的信息会很棒。 我的背景一般是 C# 和 Java,但尝试新事物总是好的。
您需要在登录 function 中添加回调以在异步操作完成时收到通知,例如
func loginFunction(username: String, password: String, onEnded: @escaping () -> () = {}) {
var result = false
// ... other code
result = getResponse.status
// ... other code
// make sure you have this call once and definitely performed at the end,
// because your current implementation has many returns
// which prevent reporting any result
DispatchQueue.main.async {
self.loggedIn = result
self.onEnded() // << callback
}
} 所以代替电话
func AttempLogin(){
self.networkManager.loginFunction(username: self.usernameInput, password: self.passwordInput) {
// will be received at the login processed
if self.networkManager.loggedIn {
print("You're now logged on")
}
else{
print("You aren't logged in")
}
}
}
注意:实际上您不需要组或显式队列来调用,因为 URLSession 已经异步执行数据任务。
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