带有URLCredential的Swift 3 URLSession不起作用 [英] Swift 3 URLSession with URLCredential not working

问题描述

我正在执行URLSession，但是该URL需要凭据.

I am doing a URLSession, but the URL requires credentials.

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

I have this whole method here that is trying to do a URLSession with URLCredentials:

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:

and here are my URLSessionDelegate Methods:

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)

    }

在此委托方法中调试时，我会注意到:

I notice when I debug this in this delegate method:

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，并且第二次点击该行:

That this method gets called twice and when it hits this line for the second time:

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

然后我的应用程序崩溃了！如何解决此错误?

and then my app crashes! How do I fix this error?

推荐答案

当您尝试强制打开包装时，崩溃是由于challenge.protectionSpace.serverTrust为零.

the crash is due to challenge.protectionSpace.serverTrust being nil when you attempt to force unwrap it.

您应该解开serverTrust并将其处理为零.我的猜测是，当serverTrust为nil时，challenge.error具有值.

you should unwrap serverTrust and handle it being nil. my guess is that when serverTrust is nil challenge.error has a value.

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
    }
}

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