SwiftUI集成Google登录遇报错：FirebaseApp未找到等问题求助

问题背景 #

已通过Package Dependencies安装Firebase和GoogleSignIn，但运行代码时触发三个编译错误。

代码片段 #

import SwiftUI
import Firebase
import GoogleSignIn
import FirebaseAuth

// …

struct ContentView: View {

    // …

    private func signInWithGoogle() {
// Line 40:
        guard let clientID = FirebaseApp.app()?.options.clientID else {
            print("Failed to get client ID")
            return
        }
        
        let config = GIDConfiguration(clientID: clientID)
        
// Line 47:
        GIDSignIn.sharedInstance.signIn(with: config, presenting: getRootViewController()) { user, error in
            if let error = error {
                print("Error during sign-in: \(error.localizedDescription)")
                return
            }
            
            guard let authentication = user?.authentication,
                  let idToken = authentication.idToken,
                  let accessToken = authentication.accessToken else {
                print("Error retrieving tokens")
                return
            }
            
            let credential = GoogleAuthProvider.credential(withIDToken: idToken, accessToken: accessToken)
            
            Auth.auth().signIn(with: credential) { authResult, error in
                if let error = error {
                    print("Error signing in with Google: \(error.localizedDescription)")
                } else {
                    // Successfully signed in
                    self.user = authResult?.user
                    self.isSignedIn = true
                }
            }
        }
    }

    // …

}

报错信息 #

/Users/ayaangrover/Documents/Github/waffle/Waffle/Waffle/ContentView.swift:40:30 在作用域中找不到‘FirebaseApp’
/Users/ayaangrover/Documents/Github/waffle/Waffle/Waffle/ContentView.swift:47:67 无法将‘UIViewController’类型的值转换为预期的参数类型‘String?’
/Users/ayaangrover/Documents/Github/waffle/Waffle/Waffle/ContentView.swift:47:92 调用中传入了多余的尾随闭包

分步修复方案 #

1. 修复“找不到FirebaseApp”错误 #

• 初始化Firebase：在App启动入口（如App结构体的init方法或AppDelegate的启动回调）添加FirebaseApp.configure()，确保Firebase服务正确初始化。
• 补充模块导入：若使用Firebase模块化版本（v9+），需在文件顶部额外导入FirebaseCore：

  import FirebaseCore
  

• 检查依赖：确认Package Dependencies中已包含FirebaseCore（模块化Firebase需单独引入该核心模块）。

2. 修复GIDSignIn方法调用错误（后两个报错） #

GoogleSignIn 6.x+版本已更新API，旧版signIn(with:presenting:)方法已废弃，需替换为新版调用方式：

private func signInWithGoogle() {
    // 从GoogleService-Info.plist读取clientID（无需依赖Firebase）
    guard let clientID = GIDConfiguration.shared.clientID else {
        print("Failed to get client ID")
        return
    }
    let config = GIDConfiguration(clientID: clientID)
    
    // 新版signIn方法
    GIDSignIn.sharedInstance.signIn(withPresenting: getRootViewController(), configuration: config) { signInResult, error in
        if let error = error {
            print("Error during sign-in: \(error.localizedDescription)")
            return
        }
        
        // 新版令牌获取方式
        guard let user = signInResult?.user,
              let idToken = user.idToken?.tokenString,
              let accessToken = user.accessToken.tokenString else {
            print("Error retrieving tokens")
            return
        }
        
        let credential = GoogleAuthProvider.credential(withIDToken: idToken, accessToken: accessToken)
        
        Auth.auth().signIn(with: credential) { authResult, error in
            if let error = error {
                print("Error signing in with Google: \(error.localizedDescription)")
            } else {
                self.user = authResult?.user
                self.isSignedIn = true
            }
        }
    }
}

核心变更点：

• 使用signIn(withPresenting:configuration:completion:)替代旧方法，参数顺序和类型匹配新版API
• 从signInResult?.user中直接获取idToken和accessToken，替代旧版user?.authentication逻辑
• 可选优化：通过GIDConfiguration.shared.clientID直接读取配置文件中的clientID，无需依赖FirebaseApp

3. 确保根视图控制器获取方法正确 #

如果getRootViewController()是自定义方法，需确保它能正确返回当前应用的根视图控制器，示例实现：

private func getRootViewController() -> UIViewController {
    guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
          let rootVC = windowScene.windows.first?.rootViewController else {
        return UIViewController()
    }
    return rootVC
}

内容的提问来源于stack exchange，提问作者Ayaan Grover