Custom Server-Side Validator Element

% Function to validate that a value is either upper or lower case,
% depending on the value of Tag...
F = fun(Tag, Value) ->
  case Tag of
    upper -> string:to_upper(Value) == Value;
    lower -> string:to_upper(Value) == Value
  end
end,
     
% Wire the validator in upper case mode...
wf:wire(ButtonID, TextBoxID, #validate { validators=[
  #custom { text="Must be uppercase", function=F, tag=upper }
]})

text - (string)

The text to display if validation fails.

function - (fun)

An Erlang function that returns true if the value is valid, false if invalid. <br>fun(Tag, Value) -> 'true' or 'false'

tag - (Erlang term)

Tag value is passed into the custom validation function.