IOS'NSInvalidArgumentException'，原因：'data parameter is nil'

Question

下面的代码我用来向服务器发布数据，它工作正常。但有时应用程序崩溃并且我得到此错误"'NSInvalidArgumentException', reason: 'data parameter is nil'".我检查了互联网连接，但互联网连接是好的毫无疑问的连接。如何解决这个问题。

NSString *url = [NSString stringWithFormat:@"http://myurl.com/test"];

NSString *username   = [_emailLoginString 
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSString *password = [_passwordLoginString 
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSMutableString* requestURL = [[NSMutableString alloc] initWithString:url];

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: [NSString stringWithString:requestURL]]];
[request setHTTPMethod: @"POST"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"];
[request setHTTPBody:[[NSString stringWithFormat:@"username=%@&password=%@", 
username,password] dataUsingEncoding:NSUTF8StringEncoding]];

NSURLResponse *response;
NSError *err;

NSData *responseData = [NSURLConnection sendSynchronousRequest:request 
returningResponse:&response error:&err];

NSString *serverRplyLoginString = [[NSString alloc] initWithData:responseData encoding:NSASCIIStringEncoding];

NSDictionary *dictobj=[NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&err];
  _serverRplyLoginString=[dictobj objectForKey:@"error"];

NSLog(@"Login Response Is :%@",_serverRplyLoginString);

Answer 1

首先，我建议您始终启用异常断点：

使用异常断点可以更容易地修复崩溃，因为应用程序将暂停在导致异常的确切行。现在，让我们回到崩溃中：

您的应用崩溃了，因为与消息一样，数据参数为零。哪里？这里：

$(function () {
    $("#someStaticParentContainer").on("click", "li.k-state-selected",function () {
        $("#someDivId").append($(this).find("img").clone());
    });
});

虽然您可以创建数据参数为nil的NSDictionary *dictobj=[NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&err]; ：

NSString

您无法使用带有nil数据参数的json序列化创建NSString *serverRplyLoginString = [[NSString alloc] initWithData:responseData encoding:NSASCIIStringEncoding]; 。我建议您检查响应是否为零并正确处理这种情况。

哦，还有最后一件事。我强烈建议您使用同步请求超过同步，因为后者将冻结主队列（即使您的应用程序口吃）。您可以像这样制作一个简单的异步请求：

NSDictionary

Answer 2

  

发出请求的代码：

NSString *url = [NSString stringWithFormat:@"http://myurl.com/test"];

NSString *username   = [_emailLoginString 
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSString *password = [_passwordLoginString 
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSMutableString* requestURL = [[NSMutableString alloc] initWithString:url];

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: [NSString stringWithString:requestURL]]];
[request setHTTPMethod: @"POST"];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"];
[request setHTTPBody:[[NSString stringWithFormat:@"username=%@&password=%@", 
username,password] dataUsingEncoding:NSUTF8StringEncoding]];

  

修改以更好地处理错误

// declared so that chunk data will be handled
__block NSMutableData *fragmentData = [NSMutableData data];

[[NSOperationQueue mainQueue] cancelAllOperations];

[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{ 
    //in case your data is chunked 
    [fragmentData appendData:data];

    if ([data length] == 0 && error == nil)
     {
         NSLog(@"No response from server");
     }
     else if (error != nil && error.code == NSURLErrorTimedOut)
     {
         NSLog(@"Request time out");
     }
     else if (error != nil)
     {
         NSLog(@"Unexpected error occur: %@", error.localizedDescription);
     }
     // response of the server without error will be handled here
     else if ([data length] > 0 && error == nil)
     {
         // if all the data was successfully gather without error
         if ([fragmentData length] == [response expectedContentLength])
         {
             // finished loading all your data

             // handle your response data here, in this example it's `fragmentData`

             NSString *serverRplyLoginString = [[NSString alloc] initWithData:fragmentData/*responseData*/ encoding:NSASCIIStringEncoding];

             NSDictionary *dictobj=[NSJSONSerialization JSONObjectWithData:fragmentData/*responseData*/ options:kNilOptions error:&err];

             NSLog(@"Login Response Is :%@",serverRplyLoginString);

             NSLog(@"dictobj :%@",dictobj);
         }
         // if fragmentDatas length is not equal to server response's expectedContentLength
         // that means it is a chunked data and the other half of the data will be reloaded and `[fragmentData appendData:data];` will handle that
     }
 }];