parsing NSString data-getting null value

Question

I am parsing and NSString value but getting null in console. Please help me with the issue.

NSString *responseData = [[NSString alloc] initWithData:_responseData encoding:NSASCIIStringEncoding];
NSLog(@"Data: %@", responseData);
NSData *data = [responseData dataUsingEncoding:NSUTF8StringEncoding];

id json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSDictionary *res = [json objectForKey:@"demo"];
NSLog(@"res is %@",res);  

Answer 1

I was having a similar problem in one of my projects. I was trying to create NSString from NSData(response from webservice) and i was getting a nil. I found out that using NSASCIIStringEncoding when creating the String solved my problem. It turns out that even though UTF8 has all ASCII chars, char * may not line up correctly for certain characters and by default the init methods do nonlossy encoding which means that nil gets returned when an unexpected char is encountered. For your case this could be your code.

NSString *responseData = [[NSString alloc] initWithData:_responseData encoding:NSASCIIStringEncoding];
NSLog(@"Data: %@", responseData);
NSData *data = [responseData dataUsingEncoding:NSASCIIStringEncoding];
id json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSDictionary *res = [json objectForKey:@"demo"];
NSLog(@"res is %@",res);  

NOTE: I am not sure why you are doing all the _responseData->data conversion. If you are doing that just to deserialize your _responseData to json object, you could use it directly in NSJSONSerialization. As below.

id json = [NSJSONSerialization JSONObjectWithData:_responseData options:0 error:nil];

For more information check out this link.