Silverstripe assumes SiteTree relation is to Parent? - orm

Question

My (partial) DataObject:
class InternalExternalLink extends DataObject {
private static $db = array(
'ExternalLink' => 'VarChar(256)',
'LinkLabel' => 'VarChar(256)',
"LinkType" => "Enum(array('Internal', 'External','Attachment'))"
);
private static $has_one = array(
'InternalLink' => 'SiteTree',
'Attachment' => 'File'
);
function getCMSFields() {
$fields = new FieldList(array(
$internal = DropdownField::create("InternalLinkID", "Choose a page", SiteTree::get()->map()->toArray())->setEmptyString("-- choose --"),
));
return $fields;
}
Add I add this to Page:
class Page extends SiteTree {
private static $has_many = array(
'Links' => 'InternalExternalLink'
);
function getCMSFields() {
$fields = parent::getCMSFields();
$gridField = new GridField('Links', 'Links', $this->Links(), GridFieldConfig_RecordEditor::create());
$fields->addFieldsToTab('Root.Main', $gridField);
return $fields;
}
The problem is when adding Links via the gridfield it automatically assumes that the Link.InternalLink is the parent page, rather than any page, and hides the page select drop down. E.g. if I am editing the about-us page then every Link dataobject I add via the gridfield automatically sets its InternalLink to the about-us page.
How do I change this assumption to allow me to select any page via the dropdown?

Answer 1

Try this:
1) Give the DataObject a "Parent" relation:
class InternalExternalLink extends DataObject {
private static $has_one = array(
'Parent' => 'DataObject',
'InternalLink' => 'SiteTree',
'Attachment' => 'File'
);
...
}
2) Specify "Parent" in the page's has_many:
class LinkTestPage extends SiteTree {
private static $has_many = array(
'Links' => 'InternalExternalLink.Parent'
);
...
}

Answer 2

The problem here is the relation on InternalExternalLink is to SiteTree whereas you're trying to define a relationship back to it on Page. As there's no has_one from InternalExternalLink to Page, and you're using a slightly older version of 3.1, the default has_one of Parent is looked for.
To solve this, you can either change the InternalLink relation to point to Page instead of SiteTree or use a DataExtension to add the has_many relation on to SiteTree.