title: IOS: check a textfield text
body: <p>In a textfield I should write a number: this number can be with point (10.23) or without poin (10); but I should to check that this number is a number and not a word. Can I check if in a textfield there is a number instead a word?
  Example: if I write a word instead a number I want an nslog that say that there is an error.</p>