CODEWITHSUNDEEP
iosiphoneswift
CeliaLi
CeliaLi

Reputation: 313

'NSError' is not convertible to 'NSError?'

I just upgraded to Xcode 6.3 and Swift 1.2, and am in the process of updating syntaxes. In my project I use TCBlobDownloadSwift for some regular downloading tasks. After the update, I get a compiler error "'NSError' is not convertible to 'NSError?'"from the following method from the framework:

func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError sessionError: NSError?) {
        let download = self.downloads[task.taskIdentifier]!
        var error: NSError? = sessionError ?? download.error

        // Handle possible HTTP errors
        if let response = task.response as? NSHTTPURLResponse {
            // NSURLErrorDomain errors are not supposed to be reported by this delegate
            // according to https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/URLLoadingSystem/NSURLSessionConcepts/NSURLSessionConcepts.html
            // so let's ignore them as they sometimes appear there for now. (But WTF?)
            if !validateResponse(response) && (error == nil || error!.domain == NSURLErrorDomain) {
                error = NSError(domain: kTCBlobDownloadErrorDomain,
                                  code: TCBlobDownloadError.TCBlobDownloadHTTPError.rawValue,
                              userInfo: [kTCBlobDownloadErrorDescriptionKey: "Erroneous HTTP status code: \(response.statusCode)",
                                         kTCBlobDownloadErrorFailingURLKey: task.originalRequest.URL,
                                         kTCBlobDownloadErrorHTTPStatusKey: response.statusCode])
            }
        }

        // Remove reference to the download
        self.downloads.removeValueForKey(task.taskIdentifier)

        dispatch_async(dispatch_get_main_queue()) {
            download.delegate?.download(download, didFinishWithError: error, atLocation: download.resultingURL)
            return
        }
    }
}

Somehow I cannot assign a NSError(initialized with initWithDomain:code:userInfo)to error(NSError?) anymore. What has changed in Swift 1.2? How should I fix this?

Returning a NSError? seems to be normal among networking related functions, especially if objC libraries were used. I'm now confused about the best way to carry an error, should I use NSError, NSError? or NSErrorPointer?

Upvotes: 2

Views: 1000

Answers (1)

CeliaLi
CeliaLi

Reputation: 313

So I fixed the problem, turns out there's nothing wrong with assigning an optional value to a NSError. the userInfo dictionary I pass to NSError's init method takes a URL from NSURLSessionTask's OriginalRequest,which is a NSURLRequest. this property is now changed to NSURL?. I changed to task.originalRequest.URL! and it worked.

I guess I will continue using NSError? to pass down errors.

Upvotes: 1

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