为什么我的 swift 代码执行不正常？Firebase 身份验证

Question

我打电话Authenticator.loginUser()时期望该方法将登录用户然后调用getCurrentUser(). 基于打印输出，getCurrentUser()首先执行。有没有办法强制它按顺序执行？

class Authenticator: ObservableObject {
        
        @Published var currentUser: UserProfile = UserProfile()
        @Published var user: String = ""
        @Published var documentId: String = ""
            
        func loginUser (email: String, password: String, viewModel: UsersViewModel) {
            FirebaseAuth.Auth.auth().signIn(withEmail: email, password: password, completion: { result, error in
                
                guard error == nil else {
                    print ("error: \(error!)")
                    return
                }
                print ("user signed in")
            })
            self.user = self.getCurrentUser(viewModel: viewModel)
        }
        
        func getCurrentUser(viewModel: UsersViewModel) -> String {
            guard let userID = Auth.auth().currentUser?.uid else {
                return ""
            }
            
            viewModel.users.forEach { i in
                if (i.userId == userID) {
                    currentUser = i
                }
            }
            
            documentId = currentUser.documentId!
            print("auth.documentId \(documentId)")
            return userID
        }
        
    }

Answer 1

FirebaseAuth.Auth.auth().signIn是异步的- 它在后台运行，而不是在主线程上。这意味着signIn将在未来的某个时间调用。

一种解决方案是将调用getCurrentUser放在完成块中：

func loginUser(email: String, password: String, viewModel: UsersViewModel) {
    FirebaseAuth.Auth.auth().signIn(withEmail: email, password: password, completion: { result, error in
        guard error == nil else {
            print("error: \(error!)")
            return
        }
        print("user signed in")
        self.user = self.getCurrentUser(viewModel: viewModel) // move here
    })
}