Page Controller

MyPage.ss

 <% if $Messages.Count %>
                    <% loop $Messages %>
                        <% include Message isSearch=$Top.isSearch %>
                    <% end_loop %>
                <% end_if %>

MyPage_edit.ss

<!-- Both edit and new will hit this template -->
$EditForm

MyPageController.php

<?php

namespace Firesphere\StripeSlack\Controllers;

use Firesphere\StripeSlack\Forms\SearchForm;
use Firesphere\StripeSlack\Helpers\Emojis;
use Firesphere\StripeSlack\Models\Channel;
use Firesphere\StripeSlack\Models\Message;
use Firesphere\StripeSlack\Models\SlackUser;
use PageController;
use SilverStripe\Control\HTTPRequest;
use SilverStripe\ORM\ArrayList;
use SilverStripe\ORM\DataList;
use SilverStripe\ORM\PaginatedList;
use SilverStripe\View\ArrayData;

/**
 * Class \Firesphere\StripeSlack\Controllers\SlackPageController
 *
 */
class SlackPageController extends PageController
{
    private static $allowed_actions = [
        'edit',
    ];
    private static $url_handlers = [
        'edit' => 'edit',
        'new' => 'edit'
    ];
    
    // The $Messages in the template will hit this method
    public function getMessages()
    {
        $channelID = Controller::curr()->getRequest->param('ID');

        /** @var Channel $channel */
        $channel = Channel::get()->filter(['Name' => $channelID])->first();
        if (!$channel) {
            $channel = Channel::get()->filter(['SlackId' => $channelID])->first();
        }
        $vars = Controller::curr()->getRequest->getVars();
        unset($vars['message']);
        if (!$channel) {
            return $this->httpError(404, 'Channel not found');
        }
        $messages = $channel->Messages()->filter(['ParentID' => 0]);
        $vars = Controller::curr()->getRequest()->getVars();
        // Returns the "Messages", to be looped in the template. The request should be available
        return PaginatedList::create($messages, $this->getRequest);
    }
    
    public function edit()
    {
        return $this;
    }
    
    public function getEditForm()
    {
        $data = [];
        $this->getRequest->getSession->set('ObjectType', 'new');
        if ($id = $this->getRequest()->URLParams['ID']) {
            $data = MyObject::get()->byID($id);
            $this->getRequest->getSession->set('ObjectType', $id);
        }
        
        $form = Form::create($this, __FUNCTION__, $myGeneratedFieldList, $myGeneratedFieldActions);
        
        $form->populateWith($data);
    }
    
    public function handleForm($data, $form)
    {
        $fromSession = $this->getRequest()->getSession()->get('ObjectType');
        if ($fromSession === 'new') {
            // handle new submission
        } else {
            // Handle edit submission
        }
    }
      
}