Getting Form Data in edit-view with JTable which is joined?

Question

i'm stuck with a problem of joined tables and retrieving Form-Data how it "should be" in best-practise-terms of Joomla!

I'm following the Joomla!-standards as far as my knownledge reaches, and the goal is to write this component "as if" it was native Joomla!-Code.

So what i have is the following COM_COMPONENT\models\release.php

<?php
defined('_JEXEC') or die;

class DojoMusicLibraryModelRelease extends JModelAdmin
{
    public function getTable( $type = 'Releases', $prefix = 'DojoMusicLibraryTable', $config = array() )
    {
        return JTable::getInstance($type, $prefix, $config);
    }

    public function getForm( $data = array(), $loadData = true )
    {
        $options = array('control' => 'jform', 'load_data' => $loadData);
        $form =  $this->loadForm('releases', 'release', $options);

        if (empty($form)) {
            return false;
        }

        return $form;
    }

    protected function loadFormData()
    {
        $app = JFactory::getApplication();
        $data = $app->getUserState('com_dojomusiclibrary.edit.release.data', array());

        if (empty($data)) {
            $data = $this->getItem();
        }

        return $data;
    }
}

And in COM_COMPONENT\tables\releases.php

<?php
defined('_JEXEC') or die;

class DojoMusiclibraryTableReleases extends JTable
{
    public $id;
    public $title;
    public $alias;
    public $artist_id;
    public $release_date_digital;
    public $release_date_physical;
    public $ean;
    public $catalog_number;
    public $promotional_text;
    public $is_compilation;
    public $format_id;
    public $release_status;
    // TODO: This tracklist should not be in this table, but only an id referring to it
    public $tracklist;
    public $created_at;
    public $modified_at;
    public $state;
    public $publish_up;
    public $publish_down;

    public function __construct($db)
    {
        parent::__construct('#__dojomusiclibrary_releases', 'id', $db);
    }
}

So now, as you can see from the comment in the latter code-example, the variable $tracklist is a field in the releases-table in my MySQL by now. As i got a "repeatable"-field-type, there is JSON inside of that field, and it works so far.

But the component is meant to hold another MySQL-table called "tracks", which holds all tracks of all releases and should be joined by a tracklist-id to the releases table, so that we have the following three tables:

• releases (holds all the data, that is strictly bound to a single release/album/ep...)
• tracklists (is an 1-to-m relation table, that has a tracklist_id, which is joined with the release and joins all single track_ids that belong to the tracklist)
• tracks (holds all the track data, such as track_title, duration, genre and so on, while every track has an unique id, which can be joined to the tracklists)

As you can see this is getting more and more complex (especially if you consider that this is not the only part of the component, where this kind of joining tables for a single JForm will be needed).

Excerpt from the COM_COMPONENT\models\forms\release.xml

<!-- CATALOG NUMBER -->
<field name="catalog_number" type="text"
       label="COM_DOJOMUSICLIBRARY_FORM_FIELD_CATALOG_NUMBER_LABEL"
       description="COM_DOJOMUSICLIBRARY_FORM_FIELD_CATALOG_NUMBER_DESC" />

So now, as JForm seemingly expects something coming from the JTable since the release.xml binds the field-name to the naming of the variable in the JTable-Class, i do not really know how to deal with that, given that the data, that should be passed in one Form is coming from different tables.

So in summary i got different problems as far as i can see:

1. How can i manage to join tables for (best practice and right) treatment of the JForm Standard in Joomla! ?

2. Since i use a repeatable-field-type to manage the tracklist, data will be stored into a JSON and saved to the database in only one field. I need this repeatable solution since every release has n tracks with more than one information (track_no, title, genre...) and thanks to Joomla there is finally a native way to handle such cases. BUT: Before saving them to the database the JSON must be split up into it's single values and be assigned to the proper fields in the tracks-table.

Okay... I know this is a huuuuuge question maybe... but since i'm totally stuck, I'd be happy about any advice for at least one of the issues :D

Thanks in advance :)