Swift：通过发布请求获取JSON接收

Question

let task = URLSession.shared.dataTask(with: postRequest) { data, response, error in 
     guard let data = data, error == nil else { 
      print(error?.localizedDescription ?? "NoData") 
      return 
     } 
     let jsonString = String(data: data, encoding: String.Encoding.utf8)! 
     self.submitView.text = jsonString 
    } 
    task.resume() 

我试图访问此帖子请求的返回值。我设置了一个断点，并看到jsonString的确获得了正确的值。然而，我尝试self.submitView.text设置为任何东西，我得到这个错误：

2017-06-21 14:20:16.062815-0400 Button[958:197756] This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes. 
Stack:(
    0 CoreFoundation      0x0000000191c82ff8 <redacted> + 148 
    1 libobjc.A.dylib      0x00000001906e4538 objc_exception_throw + 56 
    2 CoreFoundation      0x0000000191c82f28 <redacted> + 0 
    3 Foundation       0x0000000192874338 <redacted> + 128 
    4 Foundation       0x00000001926bc9f8 <redacted> + 36 
    5 UIKit        0x0000000197daf76c <redacted> + 816 
    6 UIKit        0x0000000197dbb668 <redacted> + 1740 
    7 UIKit        0x0000000197dbaf84 <redacted> + 828 
    8 UIKit        0x0000000197df90f4 <redacted> + 256 
    9 UIKit        0x0000000197df1818 <redacted> + 116 
    10 UIKit        0x00000001987ec308 <redacted> + 48 
    11 UIKit        0x0000000197e5d880 <redacted> + 280 
    12 UIFoundation      0x0000000197cdb238 <redacted> + 7012 
    13 UIFoundation      0x0000000197cdc0c8 <redacted> + 52 
    14 UIFoundation      0x0000000197d0eb70 <redacted> + 48 
    15 UIKit        0x0000000197e5d85c <redacted> + 244 
    16 UIFoundation      0x0000000197ce0214 <redacted> + 2172 
    17 UIFoundation      0x0000000197d0b058 <redacted> + 240 
    18 UIFoundation      0x0000000197d2f474 <redacted> + 160 
    19 UIFoundation      0x0000000197d2ebb4 <redacted> + 92 
    20 UIKit        0x0000000197e60500 <redacted> + 252 
    21 UIKit        0x0000000197e603e4 <redacted> + 196 
    22 Button        0x0000000100061e24 _TFFC6Button14ViewController12submitTappedFT_T_U_FTGSqV10Foundation4Data_GSqCSo11URLResponse_GSqPs5Error___T_ + 784 
    23 Button        0x0000000100062468 _TTRXFo_oGSqV10Foundation4Data_oGSqCSo11URLResponse_oGSqPs5Error____XFdCb_dGSqCSo6NSData_dGSqS1__dGSqCSo7NSError___ + 224 
    24 CFNetwork       0x000000019228c34c <redacted> + 32 
    25 CFNetwork       0x00000001922a4048 <redacted> + 148 
    26 Foundation       0x0000000192751814 <redacted> + 16 
    27 Foundation       0x0000000192696770 <redacted> + 96 
    28 Foundation       0x0000000192686b28 <redacted> + 612 
    29 Foundation       0x0000000192753bb0 <redacted> + 228 
    30 libdispatch.dylib     0x0000000100a6da10 _dispatch_client_callout + 16 
    31 libdispatch.dylib     0x0000000100a7b2e8 _dispatch_queue_serial_drain + 1140 
    32 libdispatch.dylib     0x0000000100a71634 _dispatch_queue_invoke + 852 
    33 libdispatch.dylib     0x0000000100a7d630 _dispatch_root_queue_drain + 552 
    34 libdispatch.dylib     0x0000000100a7d39c _dispatch_worker_thread3 + 140 
    35 libsystem_pthread.dylib    0x0000000190d43100 _pthread_wqthread + 1096 
    36 libsystem_pthread.dylib    0x0000000190d42cac start_wqthread + 4 
) 
2017-06-21 14:20:16.085280-0400 Button[958:197756] This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread. This can lead to engine corruption and weird crashes. 
Stack:(
    0 CoreFoundation      0x0000000191c82ff8 <redacted> + 148 
    1 libobjc.A.dylib      0x00000001906e4538 objc_exception_throw + 56 
    2 CoreFoundation      0x0000000191c82f28 <redacted> + 0 
    3 Foundation       0x0000000192874338 <redacted> + 128 
    4 Foundation       0x00000001926bc9f8 <redacted> + 36 
    5 UIKit        0x0000000197eb18e0 <redacted> + 564 
    6 UIKit        0x0000000197db0138 <redacted> + 224 
    7 UIKit        0x0000000197daf8d0 <redacted> + 120 
    8 Foundation       0x00000001926bca7c <redacted> + 168 
    9 UIKit        0x0000000197daf76c <redacted> + 816 
    10 UIKit        0x0000000197dbb668 <redacted> + 1740 
    11 UIKit        0x0000000197dbaf84 <redacted> + 828 
    12 UIKit        0x0000000197df90f4 <redacted> + 256 
    13 UIKit        0x0000000197df1818 <redacted> + 116 
    14 UIKit        0x00000001987ec308 <redacted> + 48 
    15 UIKit        0x0000000197e5d880 <redacted> + 280 
    16 UIFoundation      0x0000000197cdb238 <redacted> + 7012 
    17 UIFoundation      0x0000000197cdc0c8 <redacted> + 52 
    18 UIFoundation      0x0000000197d0eb70 <redacted> + 48 
    19 UIKit        0x0000000197e5d85c <redacted> + 244 
    20 UIFoundation      0x0000000197ce0214 <redacted> + 2172 
    21 UIFoundation      0x0000000197d0b058 <redacted> + 240 
    22 UIFoundation      0x0000000197d2f474 <redacted> + 160 
    23 UIFoundation      0x0000000197d2ebb4 <redacted> + 92 
    24 UIKit        0x0000000197e60500 <redacted> + 252 
    25 UIKit        0x0000000197e603e4 <redacted> + 196 
    26 Button        0x0000000100061e24 _TFFC6Button14ViewController12submitTappedFT_T_U_FTGSqV10Foundation4Data_GSqCSo11URLResponse_GSqPs5Error___T_ + 784 
    27 Button        0x0000000100062468 _TTRXFo_oGSqV10Foundation4Data_oGSqCSo11URLResponse_oGSqPs5Error____XFdCb_dGSqCSo6NSData_dGSqS1__dGSqCSo7NSError___ + 224 
    28 CFNetwork       0x000000019228c34c <redacted> + 32 
    29 CFNetwork       0x00000001922a4048 <redacted> + 148 
    30 Foundation       0x0000000192751814 <redacted> + 16 
    31 Foundation       0x0000000192696770 <redacted> + 96 
    32 Foundation       0x0000000192686b28 <redacted> + 612 
    33 Foundation       0x0000000192753bb0 <redacted> + 228 
    34 libdispatch.dylib     0x0000000100a6da10 _dispatch_client_callout + 16 
    35 libdispatch.dylib     0x0000000100a7b2e8 _dispatch_queue_serial_drain + 1140 
    36 libdispatch.dylib     0x0000000100a71634 _dispatch_queue_invoke + 852 
    37 libdispatch.dylib     0x0000000100a7d630 _dispatch_root_queue_drain + 552 
    38 libdispatch.dylib     0x0000000100a7d39c _dispatch_worker_thread3 + 140 
    39 libsystem_pthread.dylib    0x0000000190d43100 _pthread_wqthread + 1096 
    40 libsystem_pthread.dylib    0x0000000190d42cac start_wqthread + 4 
) 
2017-06-21 14:20:16.088842-0400 Button[958:197756] *** Assertion failure in void _UIPerformResizeOfTextViewForTextContainer(NSLayoutManager *, UIView<NSTextContainerView> *, NSTextContainer *, NSUInteger)(), /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIFoundation/UIFoundation-491.7/UIFoundation/TextSystem/NSLayoutManager_Private.m:1577 
2017-06-21 14:20:16.089727-0400 Button[958:197756] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Only run on the main thread!' 
*** First throw call stack: 
(0x191c82fe0 0x1906e4538 0x191c82eb4 0x19271a78c 0x197cd93f8 0x197cd90d8 0x197d07e88 0x197d0b188 0x197d2f474 0x197d2ebb4 0x197e60500 0x197e603e4 0x100061e24 0x100062468 0x19228c34c 0x1922a4048 0x192751814 0x192696770 0x192686b28 0x192753bb0 0x100a6da10 0x100a7b2e8 0x100a71634 0x100a7d630 0x100a7d39c 0x190d43100 0x190d42cac) 
libc++abi.dylib: terminating with uncaught exception of type NSException 

好像我不能分配给self.submitView.text“任务”的范围内任何东西。任何想法为什么？

编辑： 这是服务器在发送请求时返回的内容。

"{\"raw\":\"schedule for John in New York on Monday\",\"location\":\"New York\",\"date\":\"Mon, June 26\",\"name\":\"john\",\"errorResponse\":null,\"stripTest\":\"for John in new york on Monday\"}"

这是我的代码如下所示：

do { let info = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String : Any] DispatchQueue.main.async { self.submitView.text = info?["name"] as! String } } catch { DispatchQueue.main.async { self.submitView.text = "ERROR" } }

“ERROR” 不再印刷，但 “信息” 似乎有0键/值对，从而不执行打印作业。

UPDATE：

print(try? JSONSerialization.jsonObject(with: data, options: []))版画 “无”

后者打印：

Optional("\"{\\\"raw\\\":\\\"Schedule for John in New York on Monday\\\",\\\"location\\\":\\\"new york\\\",\\\"date\\\":\\\"6/26/2017 12:00:00 AM\\\",\\\"name\\\":\\\"john\\\",\\\"errorResponse\\\":null,\\\"stripTest\\\":\\\" for john in new york on monday \\\"}\"") 

，当我把它分配给在UI文本视图这不是什么打印..是它将转义序列转换为文字字符？

Answer 1

您正在后台线程上设置UITextField的text属性。

你需要确保所有的UI工作在主线程上完成的，你可以做到这一点使用DispatchQueue ...

DispatchQueue.main.async { 
    self.submitView.text = jsonString 
} 

更新：

的数据是一个名副其实的数据通过网络发送，您需要将其转换并反序列化。

您可以使用JSON Serialisation class像这样做：

// I create some dummy JSON string for example purposes 
let data = "{ \"name\": \"John Smith\"}".data(using: String.Encoding.utf8)! 

if let jsonObject = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:AnyObject] { 
    print(jsonObject["name"] as! String) 
} 

此尝试将数据转换成JSON对象，这在斯威夫特通常转换为一个字典对象。

有很多与Swift联网的资源可用。一个我强烈建议将iOS Networking with Swift这将需要时间公平位经历和学到了这里的东西是很多快速通过Working with JSON in Swift

UPDATE

此代码来获取工作对我来说：

let data = "{\"raw\":\"schedule for John in New York on Monday\",\"location\":\"New York\",\"date\":\"Mon, June 26\",\"name\":\"john\",\"errorResponse\":null,\"stripTest\":\"for John in new york on Monday\"}".data(using: String.Encoding.utf8)! 

if let jsonObject = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:AnyObject] { 
    print(jsonObject) 
    print(jsonObject["name"] as! String) 
}