How do you dynamically validate field input in LiveCode?

Question

I have a form in LiveCode that gathers customer details. One of those fields is for their phone number. How do I stop them typing anything other than valid phone number characters?

Answer 1

Neil's answer above is a great simple way of validating for numbers. There are two other methods you might find useful.

Note: Not 'passing' the keyDown message stops it from moving up the message path. The LiveCode field object gets the message last, so if you don't pass it, it won't be added to the field. It's a great way of performing filtering like Neil suggested.

Filter by checking if character is in a list:

on keyDown pKey
   if pKey is among the characters of "0123456789()+" then pass keyDown
end keyDown

Filter using a regular expression match:

on keyDown pKey
   put me & pKey into tPhoneNumber
   if matchText(tPhoneNumber,"[0-9]") then pass keyDown
end keyDown

In the above example you take the current contents and of the field, add the new character and check if it matches the regular expression. Using this method you can use complex regular expressions that force a certain format, length etc.

Answer 2

Like all LiveCode objects, fields receive various messages with one of them being the keyDown message. If keyDown is present in a field, it will be triggered and passed with a parameter of the current key pressed. As we now know what the key is, we can respond appropriately. -

on keyDown pKey
   if pKey is not a number then
   answer "you must type numbers only in this field"
else
    pass keyDown
  end if
end keyDown