Swift 3: URLSession / URLRequest Not Working

问题

I am still trying to convert our application from Swift 2 over to Swift 3 because I am being forced to since all of our Apple devices are now running iOS 10.

I have gone through the code conversion and thought I was doing well however, while attempting to debug my JSON issues (posted in another question), I am now dealing with requests not even being sent.

let params: [String:AnyObject] = [
    "email":"\(self.preferences.string(forKey: "preference_email")!)" as AnyObject
]
let requestParams: [String:AnyObject] = [
    "action":"601" as AnyObject,
    "params":params as AnyObject
]

do {
    let requestObject = try JSONSerialization.data(withJSONObject: requestParams, options:[])
    var request = URLRequest(url: URL(string: "http://domain.tld/path/")!)

    request.httpBody = requestObject
    request.httpMethod = "POST"

    let config = URLSessionConfiguration.default
    let session = URLSession(configuration: config)

    NSLog("Got here?")

    session.dataTask(with: request) {data, response, error in
        guard let data = data, error == nil else {
            print("error=\(error)")
            return
        }

        NSLog("Got here 3?")

        let object:JSON = JSON(data:data)

        NSLog("Object: \(object)")
    }.resume()

    NSLog("Got here 4?")
} catch {
    NSLog("Got here catch?")
}

NSLog("End of getUser")

The code above yields the following output:

2016-10-04 13:00:12.011969 OneTouch[1589:623015] [DYMTLInitPlatform] platform initialization successful
2016-10-04 13:00:12.264319 OneTouch[1589:622954] [MC] System group container for systemgroup.com.apple.configurationprofiles path is /private/var/containers/Shared/SystemGroup/systemgroup.com.apple.configurationprofiles
2016-10-04 13:00:12.265321 OneTouch[1589:622954] [MC] Reading from public effective user settings.
2016-10-04 13:00:12.295055 OneTouch[1589:622954] Got here?
2016-10-04 13:00:12.295445 OneTouch[1589:622954] Got here 4?
2016-10-04 13:00:12.295515 OneTouch[1589:622954] End of getUser
(lldb) 

Which means that the request isn't even being made. Is there some key that I have to add to the PLIST again? This is starting to get annoying.

Below is my old code and it isn't even working anymore:

let params: [String:AnyObject] = [
    "email":"\(self.preferences.string(forKey: "preference_email")!)" as AnyObject
]
let requestParams: [String:AnyObject] = [
    "action":"601" as AnyObject,
    "params":params as AnyObject
]

do {
    let requestObject = try JSONSerialization.data(withJSONObject: requestParams, options:[])
    let request = NSMutableURLRequest(url: URL(string: "http://domain.tld/path/" as String)!, cachePolicy:NSURLRequest.CachePolicy.reloadIgnoringLocalCacheData, timeoutInterval: 20)

    request.httpBody = requestObject
    request.httpMethod = "POST"

    NSLog("Got here?")

    let task = URLSession.shared.dataTask(with: request as URLRequest, completionHandler: {data, response, error in
        if error != nil {
            NSLog("Got here 2?")
        }

        NSLog("Got here 3?")

        let object:JSON = JSON(data:data!)

        NSLog("Object: \(object)")
    })

    NSLog("Got here 4?")

    task.resume()
} catch {
    NSLog("Got here catch?")
}

NSLog("End of getUser")

The code above yields the same output as the other code does!

回答1:

If you put a breakpoint immediately after calling getUser, the URLSession task's completion handler, which runs asynchronously (i.e. generally finishes later, unless the request failed immediately or was satisfied by some cached response) may not have had a chance to be called.

If you put a breakpoint inside the dataTask completion handler, you should see your data at that point.

---

Personally, I'd make sure to give getUser a completion handler so you know when it's done:

func getUser(completionHandler: @escaping (JSON?, Error?) -> Void) {
    let params = [
        "email":"\(preferences.string(forKey: "preference_email")!)"
    ]

    let requestParams: [String: Any] = [
        "action": "601",
        "params": params
    ]

    do {
        let requestObject = try JSONSerialization.data(withJSONObject: requestParams)

        var request = URLRequest(url: URL(string: "http://domain.tld/path/")!, cachePolicy: .reloadIgnoringLocalCacheData, timeoutInterval: 20)

        request.httpBody = requestObject
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.setValue("application/json", forHTTPHeaderField: "Accept")

        let task = URLSession.shared.dataTask(with: request) {data, response, error in
            guard let data = data, error == nil else {
                completionHandler(nil, error)
                return
            }

            completionHandler(JSON(data: data), nil)
        }

        task.resume()
    } catch {
        completionHandler(nil, error)
    }
}

Then when you call it, you can do something like:

getUser { json, error in
    guard let json = json else {
        print(error)
        return
    }

    // do something with json
    print(json)
}

And just put your breakpoint in getUser's completion handler. And remember that you have no assurances that the completion handler will run on the main queue or not, so you'll want to make sure to dispatch and UI or model updates back to the main queue.

来源：https://stackoverflow.com/questions/39860879/swift-3-urlsession-urlrequest-not-working