带有URLCredential的Swift 3 URLSession不起作用

Question

我正在执行URLSession，但是URL需要凭据。

我这里有整个方法，试图用URLCredentials做一个URLSession：

func loginUser(_ username: String, password: String, completion: @escaping (_ result: Bool) -> Void)
    {
        //Create request URL as String

        let requestString = String(format:"%@", webservice) as String

        //Covert URL request string to URL

        guard let url = URL(string: requestString) else {
            print("Error: cannot create URL")
            return
        }

        //Convert URL to URLRequest

        let urlRequest = URLRequest(url: url)

        print(urlRequest)

        //Add the username and password to URLCredential

        credential = URLCredential(user:username, password:password, persistence: .forSession)

        //Setup the URLSessionConfiguration

        let config = URLSessionConfiguration.default

        //Setup the URLSession

        let session = URLSession(configuration: config, delegate: self, delegateQueue: nil)

        //Prepare the task to get data.

        let task = session.dataTask(with: urlRequest, completionHandler: { (data, response, error) in

            DispatchQueue.main.async(execute: {

                if(error == nil)
                {
                    completion(true)
                }
                else
                {
                    completion(false)
                }

            })

        })

        //Run the task to get data.

        task.resume()

    }

这是我的URLSessionDelegate方法：

func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {

        if challenge.previousFailureCount > 0
        {
            completionHandler(Foundation.URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge, nil)
        }
        else
        {
            completionHandler(Foundation.URLSession.AuthChallengeDisposition.useCredential, URLCredential(trust:challenge.protectionSpace.serverTrust!))
        }

    }

    /**
     Requests credentials from the delegate in response to an authentication request from the remote server.
     */

    func urlSession(_ session: URLSession, task: URLSessionTask, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {

        completionHandler(Foundation.URLSession.AuthChallengeDisposition.useCredential,credential)

    }

我注意到在此委托方法中调试此代码时：

func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {

        if challenge.previousFailureCount > 0
        {
            completionHandler(Foundation.URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge, nil)
        }
        else
        {
            completionHandler(Foundation.URLSession.AuthChallengeDisposition.useCredential, URLCredential(trust:challenge.protectionSpace.serverTrust!))
        }

    }

该方法被调用两次，并且第二次到达该行时：

completionHandler(Foundation.URLSession.AuthChallengeDisposition.useCredential, URLCredential(trust:challenge.protectionSpace.serverTrust!))

我收到此错误：

fatal error: unexpectedly found nil while unwrapping an Optional value

然后我的应用崩溃了！ 如何解决此错误？

Answer 1

崩溃是由于在您尝试强行打开包装时， challenge.protectionSpace.serverTrust为零。

您应该解开serverTrust并将其处理为nil。 我的猜测是，当serverTrust为零challenge.error有一个值。

func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {

    if challenge.previousFailureCount > 0 {
        completionHandler(Foundation.URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge, nil)
    } else if let serverTrust = challenge.protectionSpace.serverTrust {
        completionHandler(Foundation.URLSession.AuthChallengeDisposition.useCredential, URLCredential(trust: serverTrust))
    } else {
        print("unknown state. error: \(challenge.error)")
        // do something w/ completionHandler here
    }
}

Answer 2

这是每个Swift 3的语法。

只需首先验证它在委托方法的哪一部分输入

open func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Swift.Void){

    var disposition: URLSession.AuthChallengeDisposition = URLSession.AuthChallengeDisposition.performDefaultHandling

    var credential:URLCredential?

    if challenge.protectionSpace.authenticationMethod == NSURLAuthenticationMethodServerTrust {
        credential = URLCredential(trust: challenge.protectionSpace.serverTrust!)

        if (credential != nil) {
            disposition = URLSession.AuthChallengeDisposition.useCredential
        }
        else{
            disposition = URLSession.AuthChallengeDisposition.performDefaultHandling
        }
    }
    else{
        disposition = URLSession.AuthChallengeDisposition.cancelAuthenticationChallenge
    }

    if (completionHandler != nil) {
        completionHandler(disposition, credential);
    }
}

Answer 3

这是从上面的答案中略微重构而成的，委托类检查失败的数量，使用默认值，除非质询是服务器信任类型，然后使用信任凭证调用完成：

class AuthSessionDelegate: NSObject, URLSessionDelegate {

func urlSession(_ session: URLSession,
                didReceive challenge: URLAuthenticationChallenge,
                completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {

    let authMethod = challenge.protectionSpace.authenticationMethod

    guard challenge.previousFailureCount < 1, authMethod == NSURLAuthenticationMethodServerTrust,
        let trust = challenge.protectionSpace.serverTrust else {
        completionHandler(.performDefaultHandling, nil)
        return
    }

    completionHandler(.useCredential, URLCredential(trust: trust))
}

}