Check availability in switch statement

Question

if a Enum type add new case in new os version，how to check availability in switch statement？ Like a Enum in StoreKit below

public enum Code : Int {
    public typealias _ErrorType = SKError
    case unknown
    case clientInvalid 
    case paymentCancelled 
    case paymentInvalid 
    case paymentNotAllowed
    case storeProductNotAvailable
    @available(iOS 9.3, *)
    case cloudServicePermissionDenied 
    @available(iOS 9.3, *)
    case cloudServiceNetworkConnectionFailed
    @available(iOS 10.3, *)
    case cloudServiceRevoked
}

Is below code the only solution? It's too redundant.

if #available(iOS 10.3, *) {
    switch code {
        //all cases available in 10.3
        ...
    }
} else if #available(iOS 9.3, *) {
    switch code {
       //all cases available in 9.3
       ...
    }
} else {
    switch code {
        //all cases available below 9.3
        ...
    }
}

-----------------new-------------------------

I think It's not a question. All cases writed in one switch is fine, if statement is unneccessary. Because new added cases would not called in low iOS version.

Answer 1

Usually it happens on a new versions of Xcode with fresh SDK and toolchain. So, for example Xcode 12 is bundled with iOS 14 SDK and Swift 5.3 and has a similar issues with new cases like PHAuthorizationStatus.limited which marked as available only in iOS 14 and it will break switch statement without default case.

As a workaround to make both version of Xcode 11 and Xcode 12 working I'd like to suggest following solution with checking Swift version:

    switch PHPhotoLibrary.authorizationStatus() {
    case .authorized:
        presentImagePicker()
    case .denied:
        presentAccessDeniedAlert()
    case .notDetermined:
        requestAuthorization()
    case .restricted:
        break
#if swift(>=5.3) // Xcode 12 iOS 14 support
    case .limited:
        presentImagePicker()
#endif
    @unknown default:
        assertionFailure()
    }