title: stringByTrimmingCharactersInSet: is not removing characters in the middle of the string
body: <p>I want to remove "#" from my string.</p>
  
  <p>I have tried  </p>
  
  <pre><code> NSString *abc = [@"A#BCD#D" stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"#"]];
  </code></pre>
  
  <p>But it still shows the string as "A#BCD#D" </p>
  
  <p>What could be wrong?</p>