如何在ProfileViewController中显示User对象用户名并解决相关错误

问题概述 #

• AuthViewModel的fetchUser方法调用service.fetchUser时提示Extra trailing closure passed in call错误
• ProfileViewController中currentUser?.username始终为nil，无法正常显示用户名

相关代码 #

AuthViewModel.swift #

import Foundation
import FirebaseAuth
import Firebase

class AuthViewModel: ObservableObject
{
    @Published var userSession: FirebaseAuth.User?
    @Published var currentUser: User?
    
    private var tempUserSession: FirebaseAuth.User?
    private let service = UserService()
    
    init()
    {
        self.userSession = Auth.auth().currentUser
    }
    
    func login(withEmail email: String, password: String)
    {
        Auth.auth().signIn(withEmail: email, password: password) { authResult, error in
            if let e = error
            {
                print(e.localizedDescription)
            }
            else
            {
                guard let user = authResult?.user else {return}
                self.userSession = user
                guard let uid = self.userSession?.uid else { return }
                self.service.fetchUser(withUid: uid)
                print("Did User log IN")
            }
        }
    }
    func fetchUser()
    {
        guard let uid = self.userSession?.uid else { return }
        service.fetchUser(withUid: uid) { user in <----- 错误位置：Extra trailing closure passed in call
            self.currentUser = user
        }
    }
}

ProfileViewController.swift #

import Foundation
import UIKit
import FirebaseAuth
import SwiftUI

class ProfileViewController: UIViewController
{
    var authViewModel = AuthViewModel()
    @IBOutlet weak var userNameLabel: UILabel!

    override func viewDidLoad()
    {
        navigationItem.hidesBackButton = true
        userNameLabel.text = authViewModel.currentUser?.username // 此处无法获取到用户名，值为nil
        print(userNameLabel.text)
        
    }
}

解决方案 #

1. 修复Extra trailing closure passed in call错误 #

该错误说明UserService的fetchUser(withUid:)方法定义不支持尾随闭包，需根据方法实际实现调整：

• 如果UserService.fetchUser是同步返回用户数据（无闭包参数），直接移除多余闭包，同步赋值：

  func fetchUser()
  {
      guard let uid = self.userSession?.uid else { return }
      self.currentUser = service.fetchUser(withUid: uid)
  }
  

• 如果UserService.fetchUser是异步方法（带完成闭包），检查方法定义，确保闭包参数传递正确，可显式指定参数名：

  func fetchUser()
  {
      guard let uid = self.userSession?.uid else { return }
      service.fetchUser(withUid: uid, completion: { user in
          self.currentUser = user
      })
  }
  

2. 修复currentUser?.username为nil的问题 #

问题根源：

1. AuthViewModel初始化时未调用fetchUser()，启动阶段未加载用户数据
2. login方法中调用service.fetchUser时未处理返回结果，未给currentUser赋值
3. viewDidLoad中直接读取currentUser，但用户数据加载是异步操作，此时数据尚未返回

修复步骤：

1. 在AuthViewModel初始化方法中调用fetchUser()，确保启动时加载用户信息：

   init()
   {
       self.userSession = Auth.auth().currentUser
       fetchUser() // 添加此行，初始化时获取用户数据
   }
   

2. 修复login方法，处理service.fetchUser的异步回调，赋值currentUser：

   func login(withEmail email: String, password: String)
   {
       Auth.auth().signIn(withEmail: email, password: password) { authResult, error in
           if let e = error
           {
               print(e.localizedDescription)
           }
           else
           {
               guard let user = authResult?.user else {return}
               self.userSession = user
               guard let uid = self.userSession?.uid else { return }
               // 根据UserService方法实现，添加闭包处理用户数据
               self.service.fetchUser(withUid: uid) { user in
                   self.currentUser = user
               }
               print("Did User log IN")
           }
       }
   }
   

3. 在ProfileViewController中监听currentUser的变化（利用@Published的Combine特性），确保数据更新时同步更新UI：

   import Combine // 导入Combine框架
   
   class ProfileViewController: UIViewController
   {
       var authViewModel = AuthViewModel()
       @IBOutlet weak var userNameLabel: UILabel!
       private var cancellables = Set<AnyCancellable>() // 存储订阅对象，防止被释放
   
       override func viewDidLoad()
       {
           super.viewDidLoad()
           navigationItem.hidesBackButton = true
           
           // 订阅currentUser的变化，更新UI
           authViewModel.$currentUser
               .receive(on: DispatchQueue.main) // 确保在主线程更新UI
               .sink { [weak self] user in
                   self?.userNameLabel.text = user?.username
                   print(self?.userNameLabel.text ?? "nil")
               }
               .store(in: &cancellables)
       }
   }
   

内容的提问来源于stack exchange，提问作者Branislav Fekeč