title: Writing to file overrides previous line instead of writing a new line
body: <p>So whenever I write to a file in my iPad app, it writes over the first line instead of writing to the next line down, so my file winds up only being a single line long and displays only the very last line of text. </p>
  
  <p>This is the code I'm using to write to a file:</p>
  
  <pre><code>[myString writeToFile:filePath 
             atomically:YES 
               encoding:NSASCIIStringEncoding 
                  error:nil];
  </code></pre>
  
  <p>I also tried making it so "myString" ended in the character "\n" to see if that would make it skip a line but it didn't. </p>
  
  <p>So if anyone knows what's wrong it'd really help me out.</p>