JSON序列化返回Null

Question

In our project we are taking values as json from services

Most probably my questions were asked many times but I could not find any solution.

Here is the code block:

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

  NSString *responseData = [[NSString alloc]initWithData:urlData encoding:NSUTF8StringEncoding];
  NSLog(@"Response ==> %@", responseData);
  NSError *error = nil;

  NSDictionary *jsonData = [NSJSONSerialization JSONObjectWithData:urlData options:NSJSONReadingMutableContainers error:&error];

  NSString* userID = [jsonData objectForKey:@"user_ID"];
  NSLog(@"Success: %ld userID: %ld",(long)success, (long)userID);

Log:

Response code: 200

Response ==>

{"user_ID":4}

Success: 0 userID: 0

As you can see I want to convert json object to string but when I printout content of jsonData it returns null I guess I have an issue with JSONSerializaton. Can anyone suggest solution?

Thanks, Umit

Answer 1

Just test with the following code, it's OK. You should log the error and check the response data, it may contain some invalid encoding.

const char *jsonStr = "{\"user_ID\":4}\n";
NSData *jsonData = [NSData dataWithBytes:jsonStr length:strlen(jsonStr)];
NSError *error = NULL;
NSDictionary *jsonObj = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];
NSNumber *userIDObj = [jsonObj objectForKey:@"user_ID"];
NSInteger userID = [userIDObj integerValue];
NSLog(@"=========>User ID: %d", userID);