Converting switch-as from Switch to Objective-C - ios

Question

My question is regarding this sample code from Apple.
How do I convert this switch statement using the as keyword to an Objective-C equivalent? I'm just interested in the case statements.
func authorizationController(controller: ASAuthorizationController, didCompleteWithAuthorization authorization: ASAuthorization) {
switch authorization.credential {
case let appleIDCredential as ASAuthorizationAppleIDCredential:
// Create an account in your system.
let userIdentifier = appleIDCredential.user
let fullName = appleIDCredential.fullName
let email = appleIDCredential.email
// For the purpose of this demo app, store the `userIdentifier` in the keychain.
self.saveUserInKeychain(userIdentifier)
// For the purpose of this demo app, show the Apple ID credential information in the `ResultViewController`.
self.showResultViewController(userIdentifier: userIdentifier, fullName: fullName, email: email)
case let passwordCredential as ASPasswordCredential:
// Sign in using an existing iCloud Keychain credential.
let username = passwordCredential.user
let password = passwordCredential.password
// For the purpose of this demo app, show the password credential as an alert.
DispatchQueue.main.async {
self.showPasswordCredentialAlert(username: username, password: password)
}
default:
break
}
}

Answer 1

In ObjC, the equivalent of this kind of as is -isKindOfClass:. You'll need to use if statements, since there's no equivalent version of switch. It would be something along these lines:
id<ASAuthorizationCredential> credential = authorization.credential;
if ([credential isKindOfClass:[ASAuthorizationAppleIDCredential class]]) {
ASAuthorizationAppleIDCredential *appleIDCredential = (ASAuthorizationAppleIDCredential *)credential;
// ...
}
else if ([credential isKindOfClass:[ASPasswordCredential class]]) {
ASPasswordCredential *passwordCredential = (ASPasswordCredential *)credential;
// ...
}
ObjC has two class-checking methods, -isKindOfClass: and -isMemberOfClass:. The "kind" version checks for the given class and all subclasses. The "member" version checks the exact class, so it can differentiate between superclasses and their subclasses if needed.