How do I retrieve the description of an underlying error in Swift?

Question

Given that I have the following Swift error:

Error Domain=SKErrorDomain Code=0 "UNKNOWN_ERROR" UserInfo={NSLocalizedDescription=UNKNOWN_ERROR, NSUnderlyingError=0x600002dfa430 {Error Domain=ASDErrorDomain Code=500 "Unhandled exception" UserInfo={NSUnderlyingError=0x600002dfa490 {Error Domain=AMSErrorDomain Code=100 "Authentication Failed" UserInfo={NSMultipleUnderlyingErrorsKey=(
    "Error Domain=AMSErrorDomain Code=2 \"An unknown error occurred. Please try again.\" UserInfo={NSLocalizedDescription=An unknown error occurred. Please try again.}",
    "Error Domain=AKAuthenticationError Code=-7003 \"(null)\""
), NSLocalizedDescription=Authentication Failed, NSLocalizedFailureReason=The authentication failed.}}, NSLocalizedFailureReason=An unknown error occurred, NSLocalizedDescription=Unhandled exception}}}

The localizedDescription for this error is UNKNOWN_ERROR , however I would like to retrieve the underlying error called Authentication Failed .

How can I retrieve this description in Swift?

Answer 1

The following code gives the last underlying error.

extension NSError {
    
    var lastUnderlyingErrorDescription: String {
        if let underlyingError = userInfo[NSUnderlyingErrorKey] as? NSError {
            return underlyingError.lastUnderlyingErrorDescription // Recursion 😎
        }
        // LocalizedFailureReason is often - but not always - more expressive than localizedDescription.
        return localizedFailureReason ?? localizedDescription
        
    }
    
}