Silverstripe: loop many_many without duplicates for a Colleagues page - silverstripe

Question

One of my sites has a staff section, set up in a holder/page pattern.
Departments are Data Objects.
Staff Profiles are Pages.
Both are a many_many relationship - a Staff Profile can have many Departments, and a Department has many Staff Profiles.
On the Staff Profile pages I want to list Colleagues from all the Departments that Staff Profile is associated with.
I can list all the colleagues names no problem, but where a colleague shares more than one department that person's name is listed for each department they also appear in. E.g. if they share two departments with the current Staff Profile, they appear twice in the Colleagues list
What I would like is for any Colleagues to only appear once in the Colleagues list.
I have tried GroupedList - this does what it is supposed to, but duplicates the groups for each instance of the colleagues appearing in the list, so I get the same results as without the group.
Does anyone have any ideas on how I can show only unique StaffProfiles when looped against Departments?

Answer 1

Here's one way of doing it:
// Department.php
class Department extends DataObject
{
private static $many_many = [
'StaffProfilePages' => 'StaffProfilePage'
];
}
// StaffProfilePage.php
class StaffProfilePage extends Page
{
private static $belongs_many_many = [
'Departments' => 'Department'
];
/**
* Fetch all StaffProfilePages that aren't this one, and share
* at least one department with this StaffProfilePage.
*
* #return DataList
*/
public function Colleagues()
{
return StaffProfilePage::get()->filter(
[
'ID:not' => $this->ID,
'Departments.ID' => $this->Departments()->column('ID')
]
);
}
}
And then access the colleagues in your template file like this (make sure to be in the context of a StaffProfilePage):
<%-- StaffProfilePage.ss --%>
<% loop $Colleagues %>
Hello I am {$Title} and I work with {$Up.Title}. <br />
<% end_loop %>
Some references:
https://docs.silverstripe.org/en/3/developer_guides/model/data_model_and_orm/#filtering-results
https://docs.silverstripe.org/en/3/developer_guides/model/searchfilters/