Joomla 2.5 component load data from 3 forms

Question

I'm still creating a component for Joomla 2.5 that have 4 forms: one main form (title, description) and others 3 forms with more fields. Main form have an id autoincrement that is the foreign key for other tables.

mainTable -> PK: id
secondTable -> PK: id, FK: idMainTable
thirdTable -> PK: id, FK: idMainTable
fourTable -> PK: id, FK: idMainTable

When I try to retrieve the populate forms, the id passed over the forms is the same of main form (pk of main form).

In view.html.php

function display($tpl = null) 
    {
        // Initialiase variables.
        $this->state    = $this->get('State');
        $this->item     = $this->get('Item');
        $this->mainForm = $this->get('Form');

        // GET OTHER MODELS FOR OTHER FORMS
        $secondMod = JModel::getInstance('second', 'secondModel');
        $this->secondForm = $secondMod->getForm();

        $thirdMod = JModel::getInstance('third', 'thirdModel');
        $this->thirdForm = $thirdMod->getForm();

        $fourMod = JModel::getInstance('four', 'fourModel');
        $this->fourForm = $fourMod->getForm();

        ...

        parent::display($tpl);
    }

All forms are loaded, but the passed id is the same for mainModel, so the forms for the other 3 models are empty.

How can I get the complete form with correct loaded data and the correct relationship?

Thanks

Answer 1

SOLVED (maybe...)

In each model, I have override the getItem method like this:

public function getItem($pk = null)
{
        $item = null;

        $idMain = (int) JRequest::getVar('id');

        if ($idMain > 0)
        {
            $db =& JFactory::getDBO();
            $query = $db->getQuery(true);

            $query->select('second.*');
            $query->from('#__secondTable AS s');
            $query->innerJoin('#__firstTable AS f ON s.idFK = f.id');
            $query->where('f.id = '. (int) $idMain);

            $db->setQuery($query);
            $item =  $db->loadObject();
            return $item;
        }
}

But I have many doubts about this statement:

$idMain = (int) JRequest::getVar('id');

$pk is always null...