title: enumerateKeysAndObjectsWithOptions is not working as expected
body: <p>In which situation enumerateKeysAndObjectsWithOptions is used.For running the code for every object of nsdictionary or nsarray we can also use "for in "loop construct then what is the use of this method.Any way if i use this on nsdictionary for going through every object it is altering the output .May be some thread concept is being applied. can anybody explain the reason.</p>
  
  <p>here is a simple code what i used.</p>
  
  <pre><code> NSDictionary *dict=@{@"1":@"india",
                           @"2":@"uk",
                           @"3":@"dubai",
                           @"4":@"china"
                           };
  
  [dict enumerateKeysAndObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id key, id obj, BOOL *stop) {
  
      NSLog(@"key is %@",key);
       NSLog(@"value is %@",obj);
  
    }];
  </code></pre>
  
  <p>output:
  ] key is 3</p>
  
  <p>key is 1</p>
  
  <p>value is dubai</p>
  
  <p>key is 4</p>
  
  <p>value is china</p>
  
  <p>value is india</p>
  
  <p>key is 2</p>
  
  <p>value is uk</p>