SilverStripe dependent dropdown - x is not a valid option - php

Question

I have a simple dropdown field with 2 values and a dependent dropdown field:
public function areaForm() {
$datasource = function($val) {
if ($val =='yes') {
$areas = DataObject::get('Area', 'ParentID = 0');
return $areas->map('ID', 'Name');
}
if ($val == 'no') {
return false;
}
};
$fields = new FieldList(
TextField::create('Name', 'Area Name:'),
$dropField = DropdownField::create('isChild', 'Is this a sub Area?', array('yes' => 'Yes', 'no'=>'No' ))
->setEmptyString('Select one'),
DependentDropdownField::create('ParentSelect', 'Select Parent Area:', $datasource)
->setDepends($dropField)
->setEmptyString('Select one')
);
return new Form($this, __FUNCTION__, $fields, FieldList::create(new FormAction('doSaveArea', 'Save area')));
}
public function doSaveArea($data, $form) {
var_dump($data);
exit;
$name = $data['Name'];
$isChild = $data['isChild'];
if ($isChild === 'no') {
$area = new Area();
$area->Name = $name;
$area->ParentID = 0;
$area->write();
}
elseif ($isChild === 'yes') {
$area = new Area();
$area->Name = $name;
$area->ParentID = $data['ParentSelect'];
$area->write();
}
$this->redirectBack();
}
When ever I try to save my object by submitting the form, it gives me the same message:
Please select a value within the list provided. x is not a valid option
The values are being populated correctly. I can see them in the browser by inspecting the element. Yet if I select ID 1 for example it says "1 is not a valid option" etc for each Area object. It gets stuck at validation, doesn't even go to the action. I've done similar things in other parts of the site/other sites and they work fine.
Why is this validation incorrectly blocking the form submission and how do we fix this?

Answer 1

Seems like you just need to create an Array of your Map object.
if ($val =='yes') {
$areas = Area::get()->filter('ParentID', '0');
return $areas->map('ID', 'Name')->toArray();
}
Normally you could just use the Map object as the source for a DropdownField. But I think the DependentDropdownField has a little trouble with the Map object.