title: remove non ASCII characters from NSString in objective-c
body: <p>I have an app that syncs data from a remote DB that users populate.  Seems people copy and paste crap from a ton of different OS's and programs which can cause different hidden non ASCII values to be imported into the system.</p>
  
  <p>For example I end up with this:</p>
  
  <pre><code>Artist:â â Ioco
  </code></pre>
  
  <p>This ends up getting sent back into system during sync and my JSON conversion furthers the problem and invalid characters in various places cause my app to crash.</p>
  
  <p>How do I search for and clean out any of these invalid characters?</p>