在Apple登录中，返回的“user”凭证是永久的，但是你需要管理它的存储和使用。

以下是一个使用Swift编写的示例代码，展示了如何获取Apple登录凭证并存储它：

import AuthenticationServices

class AppleLoginManager: NSObject, ASAuthorizationControllerDelegate, ASAuthorizationControllerPresentationContextProviding {
    
    func handleAppleLogin() {
        let appleIDProvider = ASAuthorizationAppleIDProvider()
        let request = appleIDProvider.createRequest()
        request.requestedScopes = [.fullName, .email]
        
        let authorizationController = ASAuthorizationController(authorizationRequests: [request])
        authorizationController.delegate = self
        authorizationController.presentationContextProvider = self
        authorizationController.performRequests()
    }
    
    // Handle the Apple login response
    func authorizationController(controller: ASAuthorizationController, didCompleteWithAuthorization authorization: ASAuthorization) {
        if let appleIDCredential = authorization.credential as? ASAuthorizationAppleIDCredential {
            // Get the user identifier
            let userIdentifier = appleIDCredential.user
            // Store the user identifier for later use
            
            // The user identifier is permanent and can be used for future authentication
        }
    }
    
    // Handle the Apple login error
    func authorizationController(controller: ASAuthorizationController, didCompleteWithError error: Error) {
        // Handle the error
    }
    
    // Provide the presentation context for the Apple login
    func presentationAnchor(for controller: ASAuthorizationController) -> ASPresentationAnchor {
        // Return the window or view controller to present the Apple login
    }
}

在上面的示例代码中，handleAppleLogin方法触发了Apple登录请求，并在authorizationController:didCompleteWithAuthorization方法中获取了返回的user凭证。你可以在这个方法中将凭证存储在你的应用程序中，以便在以后进行身份验证。

请注意，此示例代码只展示了如何获取和存储Apple登录凭证，你还需要实现其他必要的逻辑，如处理错误和登录成功后的操作。