I have an interessting problem and hope someone can help.

It's a project for a sportsclub with several teams.

I have several dataobject with relations.

First I have the games with a relation to the lineup, who is playing in this game.
I get the data for the lineup from seasonplayer where I have the data who is playing for a certain team in a certain season.

So first I have a game and there I want the lineup, which is related to the game (of course ;) ). The relation between the game and the lineup is has_many.
I created a gridfield with the list of the players for that season. In this gridfield I want a checkbox who plays in this game. If there is an entry for a player in the table lineup for this game, the checkbox should be selected. If not empty.
Maybe someone knows how I can create that.

I tried the addon GridFieldRelationHandler, but I get an error that a RelationList is needed. I don't know how to create one, because I didn't find something helpful about that. I hope somebody can help.

Here is the code

game

class Spiele extends DataObject {
	
	private static $db = array(
	"Datum" => "Date",
	"Zeit" => "Time",
	"ToreHeim" => "Int",
	"ToreGast" => "Int",
	"Zuschauer" => "Int",
	"Gespielt" => "Boolean",
	"Stats" => "Boolean",
	"Spieldauer" => "Time"
	);
	
	private static $has_one = array(
	"Heim" => "Teams",
	"Gast" => "Teams",
	"Saison" => "Saison",
	"SpielTyp" => "SpielTyp",
	"ErgebnisArt" => "ErgebnisArt"
	);
	private static $has_many = array(
	"Tore" => "Tore",
	"Strafen" => "Strafen",
	"Aufstellung" => "Aufstellung"
	);
	 
function getCMSFields() {
		

		$fields = parent::getCMSFields();
		$fields->addFieldToTab("Root.Main", new CheckboxField("Gespielt","Gespielt"));
		$fields->addFieldToTab("Root.Main", new DropdownField("SpielTypID","Art des Spiels",SpielTyp::get()->Map("ID", "Name","-")));
		$fields->addFieldToTab("Root.Main", new TextField("Zuschauer","Zuschauer"));
		if ($this->SpielTypID == 1) {
		$fields->addFieldToTab("Root.Main", new DropdownField("HeimID","Heimteam",Teams::get()->Map("ID", "Name","-")));
		$fields->addFieldToTab("Root.Main", new DropdownField("GastID","Gastteam",Teams::get()->Map("ID", "Name","-")));	
		} else {
		$fields->addFieldToTab("Root.Main", new DropdownField("HeimID","Heimteam",Teams::get()->filter(array("Saison.ID" => $this->SaisonID))->Map("ID", "Name","-")->toArray(),1));
		$fields->addFieldToTab("Root.Main", new DropdownField("GastID","Gastteam",Teams::get()->filter(array("Saison.ID" => $this->SaisonID))->Map("ID", "Name","-")->toArray(),1));}
	 	$fields->addFieldToTab("Root.Main", new TextField("ToreHeim","Tore Heim"));
		$fields->addFieldToTab("Root.Main", new TextField("ToreGast","Tore Gast"));
	 	$fields->addFieldToTab("Root.Main", new CheckboxField("Stats","Stats"));
	 	
	/*Aufstellung */								
	 $fields->addFieldToTab('Root.Aufstellungen', new GridField(
            'Aufstellung',
            'Aufstellung',
            SpielerSaison::get()->filter(array("SaisonID" => $this->SaisonID)),
   			GridFieldConfig_RecordEditor::create()
   			
		));
		$grid->getConfig()->getComponentByType('GridFieldEditableColumns')->setDisplayFields(array(
                "Checkbox should be here"
		'Nr' => "Nr",
		'Spieler.Name' => 'Spieler'	
	));	
	 	return $fields;
	 } 

playerseason

class SpielerSaison extends DataObject {
	
	private static $db = array(
	"Nr" => "Int"	
	);
	
	private static $has_one = array(
	"Spieler" => "Spieler",
	"Saison" => "Saison",
	"Team" => "Teams"
	);

			 
function getCMSFields() {
		

		$fields = parent::getCMSFields();

	 	return $fields;
	 } 

lineup

class Aufstellung extends DataObject {
	
	private static $db = array(
	"Eiszeit" => "Varchar(6)"
	);
	
	private static $has_one = array(
	"Spiel" => "Spiele",
	"Spieler" => "Spieler"
	);

		 
function getCMSFields() {
		
echo $this->SaisonID;
		$fields = parent::getCMSFields();
	 	return $fields;
	 }
}