Validation fails

[nakhor]

I've implemented the Select2AjaxField using a DataObject class as the source on a CMS form and it all works fine except for saving - the validation fails. Looking through the code it appears that the validate method is not overridden and ends up being handled by the SingleSelectField parent which checks the selection against what it knows as the list of valid values ( which in Select2AjaxField case is blank) and cannot find the selected value and so fails the validation.

I'd suggest the validate method should be overridden in Select2AjaxField and checks that the value is a valid member of the source DataList. Happy to contribute the changes of course (once I've done them)

[nakhor]

Something like this should do it:

public function validate($validator)
{
    $value = $this->Value();
    $item = $this->getList()->find($this->getIDField(), $value);
    if($item!==null)return true;

    $validator->validationError(
        $this->name,
        _t(
            'SilverStripe\\Forms\\DropdownField.SOURCE_VALIDATION',
            "Please select a value within the list provided. {value} is not a valid option",
            array('value' => $value)
        ),
        "validation"
    );
    return false;
}