title: exception 'NSInvalidArgumentException':-[__NSArrayM objectForKey:]: unrecognized selector sent to instance 0x752c670
body: <p>I use sbjson to parse json,
  this is the Json I'm trying to parse : </p>
  
  <pre><code>{"R":"0","S":"","T":"","M":[{"C00":"2013-08-16 17:35:03"}]}
  </code></pre>
  
  <p>and this is my code:</p>
  
  <pre><code>NSString *response = [self post:@"9903" content:payload state:@""];
  NSDictionary *dict = [response JSONValue];
  NSString *result = [dict objectForKey:@"R"];
  NSLog(@"result=%@",result);
  if ([@"0" isEqualToString:result]) {
      NSDictionary *msg = [dict objectForKey:@"M"];
      NSString *C00 = [msg objectForKey:@"C00"];//here the exception Statement
      NSString *tokenString = [NSString stringWithFormat:@"%@",C00];
      NSLog(@"tokenString%@",tokenString);
      return tokenString;
  }else {
      return nil;
  }
  </code></pre>
  
  <p>the exception log:</p>
  
  <pre><code>2013-08-16 17:45:44.902 VEP[4731:c07] -[__NSArrayM objectForKey:]: unrecognized selector    sent to instance 0x7250300
  2013-08-16 17:45:44.903 VEP[4731:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM objectForKey:]: unrecognized selector sent to instance 0x7250300'
  </code></pre>
  
  <p>what's wrong? thanks for your help!</p>