Swift中CoreData UserEntity'unrecognized selector'错误排查与解决

开发集成CoreData与登录功能的App时，通过LoginView和LoginViewModel将用户信息传递至ContentView，运行时触发崩溃：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[abcText2Speech.UserEntity firstname]: unrecognized selector sent to instance 0x6000017f14c0'

相关代码片段 #

LoginViewModel中的signup方法 #

func signup()-> (UserEntity, Int){
    @StateObject var dataController = DataController.shared

    buttonState = .loading(title: "Loading", systemImage: "person")
    
    DispatchQueue.main.asyncAfter(deadline: .now()+1.5){
        if self.isValidEmail() && self.isValidPassword() && self.isValidName(){
            self.isLoggedIn = true
            dataController.addUser(firstname: self.fname, lastname: self.lname, email: self.email, password: self.password)
            
            print("signed in")
            print(dataController.savedEntities[(dataController.savedEntities.count)-1].email ?? "email")
            print(self.isLoggedIn)
            self.buttonState = .enabled(title: "Login", systemImage: "checkmark.circle")
        } else{
            self.buttonState = .disabled(title: "Fill out all fields to log in", systemImage: "exclamationmark.circle")
        }
    }
    print("Test")
    print(dataController.savedEntities[(dataController.savedEntities.count)-1].email ?? "email")
        
    return (dataController.savedEntities[(dataController.savedEntities.count)-1], 1)
}

注：此方法内的打印内容均正常输出。

SignUpView相关代码 #

ActionButton(state: $model.buttonState, onTap:{
    signup = model.signup()
    user = signup.0

                    }, backgroundColor: .primary , foregroundColor: Color(UIColor.systemBackground)
                    )
                    NavigationLink (destination: LoginView()){
                        Text("Already have a profile? Click here to Log in")
                    }
                }
            } label: {
                Label("Welcome!", systemImage: "hand.wave")
            }
            .padding()
            .textFieldStyle(.plain)
            let keyboard = abcTextViewModel()
            
            NavigationLink (destination: ContentView(viewModel: keyboard, currentUser: user) , isActive: $model.isLoggedIn){
                
                EmptyView()
            }

ContentView触发错误的代码 #

Text(currentUser.firstname ?? "name")

DataController代码 #

import Foundation
import CoreData

class DataController: ObservableObject{
static let shared = DataController()

    let container: NSPersistentContainer
    @Published var savedEntities: [UserEntity] = []
    
    init(){
        container = NSPersistentContainer(name: "Model")
        container.loadPersistentStores { description, error in
            if let error = error {
                print("Core Data failed to load: \(error.localizedDescription)")
            }
        }
        fetchUsers()
    }
    
    func fetchUsers() {
        let request = NSFetchRequest<UserEntity>(entityName: "UserEntity")
        
        do {
            savedEntities = try container.viewContext.fetch(request)
        } catch let error {
            print("Error while fetching: \(error)")
        }
    }
    
    func addUser(firstname: String, lastname: String, email: String, password: String) {
        let newUser = UserEntity(context: container.viewContext)
        newUser.firstname = firstname
        newUser.lastname = lastname
        newUser.email = email
        newUser.id = password
        saveData()
    }
    
    func saveData(){
        do {
            try container.viewContext.save()
            fetchUsers()
        } catch let error {
            print("Error saving: \(error)")
        }
    } }

崩溃触发位置（abcText2SpeechApp结构体） #

import SwiftUI

@main
struct abcText2SpeechApp: App {
    var body: some Scene {
        WindowGroup{
            SignUpView()
                .environment(\.managedObjectContext, DataController.shared.container.viewContext)
            
                
        }
        
    }
}

问题原因及解决方案 #

核心问题1：异步操作导致返回的UserEntity无效 #

signup()方法内通过DispatchQueue.main.asyncAfter延迟执行用户创建逻辑，但方法本身会立即返回当前的最后一个UserEntity——此时新用户尚未创建，返回的是旧数据（甚至可能触发数组越界）。异步代码执行完成后，传递给ContentView的仍是之前返回的无效实体，调用firstname时触发找不到方法的崩溃。

核心问题2：@StateObject声明位置错误 #

@StateObject var dataController = DataController.shared写在方法内部是错误的，@StateObject仅能用于View或ObservableObject的属性中，方法内声明会导致CoreData上下文混乱。

修复步骤 #

1. 重构LoginViewModel的signup方法
   移除方法返回值，通过@Published属性传递最新用户：

   class LoginViewModel: ObservableObject {
       // 保留原有属性（fname、lname、email、password、isLoggedIn、buttonState等）
       @Published var currentUser: UserEntity?
       let dataController = DataController.shared // 移至属性位置，使用let而非@StateObject
   
       func signup() {
           buttonState = .loading(title: "Loading", systemImage: "person")
           
           DispatchQueue.main.asyncAfter(deadline: .now()+1.5){
               guard self.isValidEmail(), self.isValidPassword(), self.isValidName() else {
                   self.buttonState = .disabled(title: "Fill out all fields to log in", systemImage: "exclamationmark.circle")
                   return
               }
               
               self.dataController.addUser(firstname: self.fname, lastname: self.lname, email: self.email, password: self.password)
               // 取最新创建的用户
               if let newUser = self.dataController.savedEntities.last {
                   self.currentUser = newUser
               }
               self.isLoggedIn = true
               self.buttonState = .enabled(title: "Login", systemImage: "checkmark.circle")
               
               print("signed in")
               print(self.dataController.savedEntities.last?.email ?? "email")
               print(self.isLoggedIn)
           }
       }
   }
   

2. 修改SignUpView的跳转逻辑
   绑定ViewModel的currentUser，确保仅当用户实体存在时才跳转：

   struct SignUpView: View {
       @StateObject var model = LoginViewModel()
       @State private var keyboard = abcTextViewModel()
   
       var body: some View {
           // 原有视图代码...
           
           ActionButton(state: $model.buttonState, onTap:{
               model.signup()
           }, backgroundColor: .primary , foregroundColor: Color(UIColor.systemBackground))
           
           NavigationLink(
               destination: ContentView(viewModel: keyboard, currentUser: model.currentUser!),
               isActive: $model.isLoggedIn,
               label: { EmptyView() }
           )
           .disabled(model.currentUser == nil) // 防止用户未创建完成时跳转
           
           NavigationLink(destination: LoginView()){
               Text("Already have a profile? Click here to Log in")
           }
       }
   }
   

3. 校验CoreData实体属性
   确认CoreData模型文件中，UserEntity确实存在名为firstname的属性（注意大小写匹配，若模型中为firstName，需同步修改代码中的调用为currentUser.firstName）。

4. 消除数组越界风险
   替换dataController.savedEntities[(dataController.savedEntities.count)-1]为dataController.savedEntities.last，并添加可选绑定判断，避免数组为空时的崩溃。

内容的提问来源于stack exchange，提问作者Jaanvi chirimar