ios - 在 Swift 中，当使用 dataTaskWithRequest 时，completionHandler 在请求超时时返回 nil NSURLResponse

Question

当我将数据发布到服务时，请求通常没有问题，但如果它花费的时间太长并且超时，在完成处理程序中，我得到的 NSURLResponse 为 nil，即使它永远不会返回 nil。

我正在使用 Swift 1.1，下面是我如何执行此操作的示例:

func postX(actionKey:String, postData:AnyObject, callBack:((data:NSData?, resp: NSURLResponse) -> Void)?) -> Void
{
    var mreq = createRequest(actionKey, method: "POST", https: true, json: true)
    if (self.dataTask != nil)
    {
        self.dataTask?.cancel()
    }
    var err: NSError?
    mreq.HTTPBody = NSJSONSerialization.dataWithJSONObject(postData, options: nil, error: &err)
    self.dataTask = self.getSession().dataTaskWithRequest(mreq, completionHandler: { (data:NSData!, resp: NSURLResponse!, error: NSError!) -> Void in

        Dlog.log("response: \(resp)")  //Prints out: response: nil
        if (error != nil)
        {
            //do something
        }
        else
        {
            //do something else
        }
    })
    if (self.dataTask != nil)
    {
        self.dataTask!.resume()
    }
}

Answer 1

dataTaskWithRequest 的 completionHandler block 中的 NSURLResponse 引用是可选的(意味着它可以 无)。如果请求超时，您希望它是 nil(因为您可能还没有收到任何响应)。

我建议将 callback 闭包的 NSURLResponse 参数更改为可选参数，就像 dataTaskWithRequest 一样。 (我可能还会返回可选的 NSError，这样您就可以检查特定的错误。)并且您可以通过查找 NSURLErrorTimedOut 来检测超时错误。

例如:

func postX(actionKey: String, postData: AnyObject, callBack: (NSData?, NSURLResponse?, NSError?) -> ()) {
    let request = createRequest(actionKey, method: "POST", https: true, json: true)

    dataTask?.cancel()   // note, we don't need `if` clause, as the `?` does everything for us

    request.HTTPBody = try! NSJSONSerialization.dataWithJSONObject(postData, options: [])

    let task = getSession().dataTaskWithRequest(request) { data, response, error in
        callBack(data, response, error)
    }

    task.resume()

    dataTask = task
}

然后你可以像这样使用它:

postX(actionKey, postData: postData) { data, response, error in

    // handle response however you want

    // did it time out?

    if error?.domain == NSURLErrorDomain && error?.code == NSURLErrorTimedOut {
        print("timed out") // note, `response` is likely `nil` if it timed out
    }

}

---

为了完整起见，Swift 3 实现可能如下所示:

func postX(actionKey: String, postData: AnyObject, callBack: (Data?, URLResponse?, NSError?) -> ()) {
    var request = createRequest(actionKey: actionKey, method: "POST", https: true, json: true)

    dataTask?.cancel()   // note, we don't need `if` clause, as the `?` does everything for us

    request.httpBody = try! JSONSerialization.data(withJSONObject: postData, options: [])

    let task = getSession().dataTask(with: request) { data, response, error in
        callBack(data, response, error)
    }

    task.resume()

    dataTask = task
}

func createRequest(actionKey: String, method: String, https: Bool, json: Bool) -> URLRequest {
    var request = URLRequest(url: ...)
    ...
    return request
}

它会被称为:

postX(actionKey: actionKey, postData: postData) { data, response, error in

    // handle response however you want

    // did it time out?

    if error?.domain == NSURLErrorDomain && error?.code == NSURLErrorTimedOut {
        print("timed out") // note, `response` is likely `nil` if it timed out
    }

}