Swift 4+Firebase注册：ViewController间Email值传递及注册实现

Hey there! Let's walk through implementing this two-step signup flow—first collecting the email, then the password, and finally submitting both to Firebase Authentication. Here's how to make it work smoothly:

Step 1: Pass Email from First View Controller to Second #

The simplest way to pass the email is by adding a public property to your second view controller, then setting that property when you navigate from the first VC.

First View Controller Code #

Assume you have a UITextField for email input and a "Next" button. We'll add validation for the email format before navigating:

// FirstViewController.swift
import UIKit

class FirstViewController: UIViewController {
    @IBOutlet weak var emailTextField: UITextField!
    
    @IBAction func nextButtonTapped(_ sender: UIButton) {
        // Validate email input
        guard let userEmail = emailTextField.text, 
              !userEmail.isEmpty, 
              isValidEmail(userEmail) else {
            showAlert(title: "Invalid Email", message: "Please enter a valid email address.")
            return
        }
        
        // Navigate to Second VC and pass the email
        guard let secondVC = storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as? SecondViewController else {
            fatalError("Couldn't instantiate SecondViewController")
        }
        secondVC.userEmail = userEmail
        navigationController?.pushViewController(secondVC, animated: true)
    }
    
    // Helper: Email format validation
    private func isValidEmail(_ email: String) -> Bool {
        let emailRegex = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
        return NSPredicate(format: "SELF MATCHES %@", emailRegex).evaluate(with: email)
    }
    
    // Helper: Reusable alert method
    private func showAlert(title: String, message: String) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default))
        present(alert, animated: true)
    }
}

Second View Controller Setup #

Add a property to store the incoming email, then set up your password field and signup button:

// SecondViewController.swift
import UIKit
import FirebaseAuth

class SecondViewController: UIViewController {
    @IBOutlet weak var passwordTextField: UITextField!
    
    // This property will hold the email from FirstVC
    var userEmail: String!
    
    @IBAction func signupButtonTapped(_ sender: UIButton) {
        // Validate password input (Firebase requires min 6 chars)
        guard let userPassword = passwordTextField.text, 
              !userPassword.isEmpty, 
              userPassword.count >= 6 else {
            showAlert(title: "Invalid Password", message: "Password must be at least 6 characters long.")
            return
        }
        
        // Submit email & password to Firebase Auth
        Auth.auth().createUser(withEmail: userEmail, password: userPassword) { [weak self] authResult, error in
            guard let self = self else { return }
            
            if let error = error {
                // Handle signup errors (e.g., email already exists, weak password)
                self.showAlert(title: "Signup Failed", message: error.localizedDescription)
                return
            }
            
            // Signup successful! Redirect to home or show success
            self.showAlert(title: "Success!", message: "Your account is created.") {
                // Replace with your home VC navigation logic
                let homeVC = self.storyboard?.instantiateViewController(withIdentifier: "HomeViewController")
                self.navigationController?.setViewControllers([homeVC!], animated: true)
            }
        }
    }
    
    // Reusable alert with optional completion
    private func showAlert(title: String, message: String, completion: (() -> Void)? = nil) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default) { _ in
            completion?()
        })
        present(alert, animated: true)
    }
}

Important Notes #

• Storyboard Setup: Make sure your second view controller has a storyboard identifier (e.g., "SecondViewController") set in the Identity Inspector.
• Firebase Configuration: Ensure you've added the GoogleService-Info.plist to your project and imported FirebaseAuth in the second VC.
• Error Handling: Firebase's createUser method returns detailed errors—we're using error.localizedDescription to show user-friendly messages.
• Memory Safety: We use [weak self] in the Firebase closure to avoid retain cycles.

内容的提问来源于stack exchange，提问作者ozy