title: Incompatible pointer type error when using NSMutableString and stringByReplacingOccurrencesOfString
body: <p>The purpose of the code shown below is to take a string from a textfield and remove commas and left parentheses, to prepare the contents for conversion to a float. For example, it takes the number 1,234,567 and changes it to 1234567.</p>
  
  <p>The code snippet works, but returns an informational error "Incompatible pointer types assigning to NSMutableString * from String *" </p>
  
  <p>When I use NSString instead of NSMutableString, I get no errors, but the returned value is an empty string. </p>
  
  <p>Using the NSMutableString methodology, what is the problem and how can I change this to eliminate the 'Incompatible pointer type" error.</p>
  
  <pre><code>NSMutableString *cleanedDataCellTest = [[NSMutableString alloc] initWithString:datacellR2C2.text];
  cleanedDataCellTest =  [cleanedDataCellTest stringByReplacingOccurrencesOfString:@"," withString:@""];
  cleanedDataCellTest =  [cleanedDataCellTest stringByReplacingOccurrencesOfString:@")" withString:@""];
  cleanedDataCellTest =  [cleanedDataCellTest stringByReplacingOccurrencesOfString:@"(" withString:@"-"];
  cleanedDataCellTest =  [cleanedDataCellTest stringByReplacingOccurrencesOfString:@" " withString:@""];
  </code></pre>