如何在使用Parse和Swift注册时设置密码规则？

import Parse

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    Parse.initialize(with: ParseClientConfiguration(block: { (configuration: ParseMutableClientConfiguration) -> Void in
        configuration.applicationId = "YOUR_APP_ID"
        configuration.clientKey = "YOUR_CLIENT_KEY"
        configuration.server = "https://your-parse-server-url.com/parse"
    }))
    return true
}

let user = PFUser()
user.username = "username"
user.password = "password"

// 设置密码规则
let passwordPolicy = PFOAuthCredentialPasswordPolicy()
passwordPolicy.minLength = 8
passwordPolicy.maxLength = 20
passwordPolicy.requireLowercase = true
passwordPolicy.requireUppercase = true
passwordPolicy.requireDigits = true
passwordPolicy.requireSpecialCharacters = true

user.passwordPolicy = passwordPolicy

user.signUpInBackground { (success: Bool, error: Error?) in
    if let error = error {
        print("Error: \(error.localizedDescription)")
    } else {
        print("User registered successfully.")
    }
}