title: [__NSArrayI replaceObjectAtIndex:withObject:]: unrecognized selector sent to instance
body: <p>I have a NSMutableArray, which I need to chance its values, but I have this error: <br>
  <strong>[__NSArrayI replaceObjectAtIndex:withObject:]: unrecognized selector sent to instance 0x5291db0</strong> <br>
  This is the declaration of my NSMutableArray: <br></p>
  
  <pre><code>NSMutableArray *selectedOptions = [NSArray arrayWithObjects:[NSNumber numberWithInteger:0], nil]; 
  </code></pre>
  
  <p>Then, I'm using replaceObjectAtIndex method, of this way: <br></p>
  
  <pre><code>[self.selectedOptions replaceObjectAtIndex:0 withObject:[NSNumber numberWithInteger:1]];
  </code></pre>
  
  <p>But I get, that error, and I'm using NSMutableArray.<br>
  Thanks</p>