title: objective c check string suffix from character set
body: <p>I'm trying to check the suffix of a string against a character set but I'm getting errors:</p>
  
  <pre><code>if ([string hasSuffix:[NSCharacterSet characterSetWithCharactersInString:@"(+-*/"])
  </code></pre>
  
  <p>What am I doing wrong, is there a correct alternative?</p>