LiveCode field level input validation

Question

How can I restrict a users input to be only numeric (allowing decimals) when typing into certain fields in a desktop application?

~Roger

Answer 1

Note that Ben's answer doesn't cover every case

• doesn't allow negative numbers
• doesn't detect the case where you type "." and there is already a trailing "." in the field
• doesn't handle pasting into the field.

You can do all those with

local sExisting

on openfield
   put the text of me into sExisting
end openfield

on textChanged
   put the selectedText && sExisting && the text of me into msg
   if the text of me is a number or me is empty then
      put the text of me into sExisting
   else
      put sExisting into me
   end if
end textChanged

NB - if you type an invalid character, the input cursor is moved to the start of the line; if you want to do anything different then you can lockscreen (as the first action in 'textChanged') and unlock when you are done.