SilverStripe 3 - next sibling using grandparent - silverstripe

Question

I have a site where I want to be able to link to the next ProductPage from the ProductPage I am currently on. I can do this for immediate siblings, but once I get to the end of that set I want to link to the next ProductRange first product. The structure is like this:
ProductArea
ProductCategory
- ProductRange
- ProductPage
- ProductPage
- ProductRange
- ProductPage
- ProductPage
ProductCategory
- ProductRange
- ProductPage
- ProductPage
- ProductRange
- ProductPage
- ProductPage
So if there is no direct sibling I need to return the next product page in order.
I'm using this for direct siblings:
function NextProduct() {
$pages = ProductPage::get()->filter(array(
'ParentID' => $this->ParentID,
'Sort:GreaterThan' => $this->Sort
))->Sort('Sort');
if ($pages) {
return $pages->First();
}
}
How do I get it working at the next level up?

Answer 1

Here is one way to do this. First we try to find the next sibling. If the next sibling does not exist we get the next parent page and get their first child.
function NextProduct() {
$pages = ProductPage::get()->filter(array(
'ParentID' => $this->ParentID,
'Sort:GreaterThan' => $this->Sort
))->Sort('Sort')->limit(1);
if ($pages->count()) {
return $pages->First();
}
$parent = $this->parent();
$parentSiblings = ProductRange::get()->filter(array(
'ParentID' => $parent->ParentID,
'Sort:GreaterThan' => $parent->Sort
))->Sort('Sort');
foreach ($parentSiblings as $parentSibling) {
$pages = ProductPage::get()->filter(array(
'ParentID' => $parentSibling->ID
))->Sort('Sort')->limit(1);
if ($pages->count()) {
return $pages->First();
}
}
return false;
}
Here is a PreviousProduct function:
function PreviousProduct() {
$pages = ProductPage::get()->filter(array(
'ParentID' => $this->ParentID,
'Sort:LessThan' => $this->Sort
))->Sort('Sort')->reverse()->limit(1);
if ($pages->count()) {
return $pages->First();
}
$parent = $this->parent();
$parentSiblings = ProductRange::get()->filter(array(
'ParentID' => $parent->ParentID,
'Sort:LessThan' => $parent->Sort
))->Sort('Sort')->reverse();
foreach ($parentSiblings as $parentSibling) {
$pages = ProductPage::get()->filter(array(
'ParentID' => $parentSibling->ID
))->Sort('Sort')->reverse()->limit(1);
if ($pages->count()) {
return $pages->First();
}
}
return false;
}