validateField method
Implementation
ValidateResult validateField(String fieldName, VerifyType type,
{dynamic preValue}) {
ValidateResult Function(dynamic, VerifyType)? _fieldCheck =
data.validateList[fieldName];
FormGroupItem _fieldData = manage[fieldName];
assert(_fieldCheck != null,
'get null check rule, please check form item fieldName');
return _fieldCheck!(preValue ?? _fieldData.getValue(), type);
}