I am creating a simple login app with custom error message display in an alert for API response failure. Below is my code

  @State private var username = ""
  @State private var password = ""
  @State private var isPresentederror = false
var body: some View {
        NavigationView{
            ZStack{
                VStack{
                   
                        
                    TextField("Username", text : $username)
                        .autocapitalization(.none)
                        .padding()
                        .frame(width:300,height: 50)
                        
                    SecureField("Password", text : $password)
                        .padding()
                        .frame(width:300,height: 50)
                        
                    Button("Login"){
                        authenticateUser(username: username, password: password)
                    }
                    
                    .foregroundColor(.white)
                    .frame(width: 300, height: 50)
                    .background(Color.blue)
                    .cornerRadius(10)
                   
                    .alert("Error", isPresented: $isPresentederror, actions: {
                      
                    }, message: {
                        Text("Something went wrong! Please try again")
                    })

                }
            }
            .navigationBarHidden(true)
        }        
    }

on Click of LOGIN button I am calling a function authenticateUser by passing username and password as a parameter Below is my authenticateUser function code

func authenticateUser(username: String, password: String){
      
     
       
        let method = "POST"
        let urlString = "http://myapi_to verify_username_password"
        
        var urlHeader=//header part goes here
        
        let json: [String: Any] = ["password": password,
                                    "username": username]
         let jsonData = try? JSONSerialization.data(withJSONObject: json)
         urlHeader.httpBody = jsonData

        URLSession.shared.dataTask(with: urlHeader) { (data, response , error) in
            
            guard let data = data else { return }
            print(String(data: data, encoding: .utf8) ?? "Invalid JSON")
            do {
                   //success code working fine
               } catch {
                   print("Error:\(error.localizedDescription)")
                   print(error)
                   isPresentederror = true
               }
            }.resume()
        
    }

success is working fine for me, but on error I am showing an alert with manual text "Something went wrong! Please try again". I want to show an error message coming from API. the line

print(String(data: data, encoding: .utf8) ?? "Invalid JSON")

in above function gives an object as below

{"timestamp":"2022-09-30T10:03:29.142 00:00","status":501,"error":"Please verify the data you have sent Found","path":"path_to_url"}

I want to show the error inside alert which is "Please verify the data you have sent Found" coming from API. I tried decoding it and UTF method but it always gives me an error. so please help me to achieve this

CodePudding user response：

You could try this approach, to ...pass response error coming from API, using a @State var errorMessage and testing the httpResponse.statusCode, such as in this example code:

struct LoginView: View {
    @State private var username = ""
    @State private var password = ""
    @State private var isPresentederror = false
    // -- here
    @State var errorMessage = "Something went wrong! Please try again"
    
    var body: some View {
        NavigationView{
            ZStack{
                VStack{
                    TextField("Username", text : $username)
                        .autocapitalization(.none)
                        .padding()
                        .frame(width:300,height: 50)
                    
                    SecureField("Password", text : $password)
                        .padding()
                        .frame(width:300,height: 50)
                    
                    Button("Login"){
                        authenticateUser(username: username, password: password)
                    }
                    .foregroundColor(.white)
                    .frame(width: 300, height: 50)
                    .background(Color.blue)
                    .cornerRadius(10)
                    
                    .alert("Error", isPresented: $isPresentederror, actions: {
                        
                    }, message: {
                        Text(errorMessage) // <-- here
                    })
                    
                }
            }
            .navigationBarHidden(true)
        }
    }
    
    func authenticateUser(username: String, password: String){

        let urlString = "https://myapi_to verify_username_password"
        
        var request = URLRequest(url: URL(string: urlString)!)
        request.httpMethod = "POST"
        
        let json: [String: Any] = ["password": password, "username": username]
        let jsonData = try? JSONSerialization.data(withJSONObject: json)
        request.httpBody = jsonData
        
        URLSession.shared.dataTask(with: request) { (data, response , error) in
            guard let data = data else { return }
            
            print(String(data: data, encoding: .utf8) ?? "Invalid JSON")

            // when the response describing the error, is returned as json
            do {
                let decoded = try JSONDecoder().decode(ApiError.self, from: data)
                errorMessage = decoded.error
                isPresentederror = true
                return
            } catch { }

            // -- here
            guard let httpResponse = response as? HTTPURLResponse else {
                errorMessage = "Unknown error"
                isPresentederror = true
                return
            }
            if (httpResponse.statusCode == 401) {
                errorMessage = "Unauthorized"
                isPresentederror = true
                return
            }
            if (405..<500 ~= httpResponse.statusCode) {
                errorMessage = "Client error"
                isPresentederror = true
                return
            }
            if (500..<600 ~= httpResponse.statusCode) {
                errorMessage = "Server error"
                isPresentederror = true
                return
            }
            // ...etc...
            
            do {
                //success code working fine
                try JSONDecoder().decode([String].self, from: data)
                //....
            } catch {
                print("Error:\(error.localizedDescription)")
                // -- here
                errorMessage = error.localizedDescription
                isPresentederror = true
            }
        }.resume()
    }
    
}

// consult the server docs
struct ApiError: Codable {
    var timestamp: String
    var status: Int
    var error: String
    var path: String
}