startsWithFn method

FieldValidator<String?, String> startsWithFn(ValueGetter<Pattern> pattern, [ MessageCallBack<String>? message ])

check if the value starts with pattern

Implementation

FieldValidator<String?, String> startsWithFn(ValueGetter<Pattern> pattern,
    [MessageCallBack<String>? message]) {
  return next((messages, value) {
    var ptr = pattern();
    return !value.startsWith(ptr)
        ? message?.call(messages, value) ??
            messages.startsWith(ptr.toString())
        : null;
  });
}