Question

So I’m not sure how to do this in a cakey way. I’ve hacked the crap out if it and now have something longer than straight php would be. I can’t find this anywhere in the docs. So here is how my tables are set up:

instruments HABTM teachers
teachers HABTM instruments
instruments_teachers is my Join table

now in the instruments_teachers table I have an extra field “type” which refers to whether it’s the teachers primary or secondary instrument.

I then have another table:

instrument_levels belongsTo instruments_teachers
instruments_teachers hasMany instrument_levels

So in summary:
A teacher can teach many instruments and instruments can belong to (or be taught) by many different teachers. Then the combination of teacher instrument is either the teachers primary or secondary instrument, and finally that combination can be taught at three different levels (defined by instrument_levels) beginning, intermediate, or advanced.

Let me know if you think there’s a better way to design the database, but it seems to make sense to me.

The problem comes when trying to use this data with cake. I can’t seem to figure it out. In my application the teachers will first select an instrument in a series of checkboxes, but the data must submit with the extra field type in the join table. Right now this is how I have the checkboxes appearing:

Controller:

$instruments = $this->Teacher->Instrument->find('list', array('fields' => array('id', 'instrument')));
$this->set(compact('instruments'));

View:

echo $this->Form->input('Instrument',array(
'label' => __('Instruments',true),
'type' => 'select',
'multiple' => 'checkbox',
'options' => $instruments,
'selected' => $this->Html->value('Instrument.Instrument'),
));

That displays all the check boxes together, but I would like more control and display each on separately (ie. a foreach loop). This doesn’t work though:

$checked = $this->Form->value('Instrument.Instrument');
echo $this->Form->label(__('Instruments', true));
foreach ($instruments as $id => $label) {
echo $this->Form->checkbox("Instrument", array(
    'checked' => (isset($checked[$id]) ? 'checked' : false),
    'hiddenField' => false,
    'value' => $id
    ));
    echo $this->Form->label("Instrument", ucfirst($label));
}

And how would I submit the extra field (“type” field) with the HABTM association? Finally I need to have checkboxes for what level the teachers can teach at. So I first need to fetch the HABTM data and then have 3 checkboxes next to the instrument. Seems easy enough, but how do I populate those check boxes after they’re added? When I fetch the data it just goes into a keyed array and doesn’t correlate to the level checkboxes. I have it in a foreach loop keyed in the form helper like so: InstrumentLevel.0.level, InstrumentLevel.1.level etc. But when the data is fetched it won’t correlate with the checkboxes correctly.

I know this was a lot, I have been working on this for a couple weeks, and I just don’t what I’m doing. If you could just lead me in the right direction I would appreciate it!

Thanks!

Answer 1

You cannot have an extra field in the join table. Each time you save your data the associations are lost, I quote

The trouble is, hasAndBelongsToMany will not support this type of
scenario because when hasAndBelongsToMany associations are saved, the
association is deleted first. You would lose the extra data in the
columns as it is not replaced in the new insert.

For that you must use hasMany Through association.

hasMany through (The Join Model)