title: Limiting text field entry to only one decimal point
body: <p>I have created a text field to enter an amount of money. I want the user to be able to enter only one decimal point. I implemented that in the <code>-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string</code> method. </p>
  
  <p>In the general case it works fine, but if backspace is pressed and the single decimal point is deleted, after that it still assumes that a decimal point has been entered, and so does not accept the decimal point again. </p>
  
  <p>I need to reset the <code>decimalPointEntered</code> flag whenever the decimal point is deleted by pressing backspace. How to do that ?</p>