title: Modification of a constant value
body: <p>I understand the differences of</p>
  
  <pre><code>NSString * const myString = @"Bar"
  </code></pre>
  
  <p>This a immutable pointer to a NSString.</p>
  
  <p>Then we have:</p>
  
  <pre><code>NSMutableString const * myMutableString = [[NSMutableString alloc]initWithString:@"Bar"]
  </code></pre>
  
  <p>This is a pointer to a const NSMutableString. The value of myMutableString should not be able to change.</p>
  
  <p>Why can then do?:
  [myMutableString append:@"Foo"];</p>
  
  <p>No compiler error, and it works. It allows me to change the value.</p>
  
  <p>In which case can then a constant object be used?</p>
  
  <p>Thanks!</p>