Guideline 4.8 - Design: Missing Sign in with Apple

In Xcode, go to your target → Signing & Capabilities → + Capability → Sign in with Apple. This enables the entitlement.

   import AuthenticationServices

   SignInWithAppleButton(.signIn) { request in
       request.requestedScopes = [.fullName, .email]
   } onCompletion: { result in
       switch result {
       case .success(let auth):
           handleAppleSignIn(auth)
       case .failure(let error):
           print("Sign in with Apple failed: \(error)")
       }
   }
   .signInWithAppleButtonStyle(.black) // or .white, .whiteOutline
   .frame(height: 50)

Place the Sign in with Apple button at the top of your login options, or at minimum the same size and position as other social login buttons:

   VStack(spacing: 12) {
       SignInWithAppleButton(...)
           .frame(height: 50)
       GoogleSignInButton()
           .frame(height: 50)
       FacebookLoginButton()
           .frame(height: 50)
   }

On first sign-in, Apple provides a user identifier, optional full name, and optional email. Cache the user identifier because Apple only sends the name and email on the FIRST authorization:

   func handleAppleSignIn(_ authorization: ASAuthorization) {
       guard let credential = authorization.credential as? ASAuthorizationAppleIDCredential else { return }
       let userId = credential.user              // Always provided
       let email = credential.email              // Only on first auth
       let fullName = credential.fullName         // Only on first auth
       // Send to your backend and create/link account
   }

Verify the Apple ID is still valid:

   ASAuthorizationAppleIDProvider().getCredentialState(forUserID: savedUserId) { state, error in
       switch state {
       case .authorized: break  // all good
       case .revoked: signOut()  // user revoked access
       case .notFound: signOut() // no credential found
       default: break
       }
   }

Apple requires using SignInWithAppleButton (SwiftUI) or ASAuthorizationAppleIDButton (UIKit). Do not create a custom button with the Apple logo.