[swift-users] Handle deprecated enum cases from a library
Dennis Weissmann
dennis at dennisweissmann.me
Sat Nov 4 09:38:49 CDT 2017
Hi swift-users,
In a project (iOS 11 only) we use Touch ID for authentication and handle errors like so:
private func handleLocalAuthenticationError(_ error: LAError) {
switch error.code {
case .userCancel, .appCancel, .systemCancel:
// Handle cancelation
case .authenticationFailed:
// Handle failure
case .passcodeNotSet:
// Handle passcode absence
case .touchIDNotEnrolled:
// Handle no Touch ID enrollment
case .touchIDNotAvailable:
// Handle no Touch ID availabe
case .touchIDLockout:
// Handle Touch ID Lockout
case .userFallback:
// Handle user fallback
case .invalidContext:
// Handle failure with invalid context
case .notInteractive:
// Handle no interaction allowed error
}
}
This worked fine until recently, when with the release of iOS 11 and the introduction of Face ID, `.touchIDLockout`, `.touchIDNotEnrolled` and `.touchIDNotAvailable` were deprecated in favor of the newly introduced `.biometryLockout`, `.biometryNotEnrolled` and `.biometryNotAvailable`.
When we link against the latest SDK we need to add those in order to compile (which is obviously good).
Now when we add those cases, the compiler shows the following warnings:
<unknown>:0: warning: 'touchIDLockout' was deprecated in iOS 11.0: use LAErrorBiometryLockout
<unknown>:0: warning: 'touchIDNotEnrolled' was deprecated in iOS 11.0: use LAErrorBiometryNotEnrolled
<unknown>:0: warning: 'touchIDNotAvailable' was deprecated in iOS 11.0: use LAErrorBiometryNotAvailable
The problem here is, that we can't remove the old ones and replace them with their new variants because for Swift the enum is then not exhaustive (which also makes sense, they're only deprecated, not removed after all).
Even though not optimal (read "really bad because not exhaustive") I thought about removing the old cases and adding a default label:
private func handleLocalAuthenticationError(_ error: LAError) {
switch error.code {
case .userCancel, .appCancel, .systemCancel:
// Handle cancelation
case .authenticationFailed:
// Handle failure
case .passcodeNotSet:
// Handle passcode absence
case .biometryNotEnrolled:
// Handle no biometry enrollment
case .biometryNotAvailable:
// Handle no biometry availabe
case .biometryLockout:
// Handle biometry Lockout
case .userFallback:
// Handle user fallback
case .invalidContext:
// Handle failure with invalid context
case .notInteractive:
// Handle no interaction allowed error
default:
// hopefully only deprecated cases
break
}
}
However, in this case the compiler warns that "Default will never be executed".
Is there any way of getting rid of these warnings (preferably the first 3 so that we don't have to have default clause)?
Thanks!
- Dennis
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