title: How to validate a string contains certain characters?
body: <p>I'm trying to check if a string contains certain characters. I was going to use regex, but my string may not have a format.</p>
  
  <p>I would like to ensure that i'm allowing only the following characters</p>
  
  <p></p>
  
  <pre>
  1. + symbol
  2. - symbol
  3. numbers 0~9
  4. (
  5. )
  6. . (dot)
  7. spaces
  </pre>
  
  <p></p>