MySQL Error with straightforward polymorphic association in CakePHP - cakephp

Question

I have 4 models, Application , Accommodation, Invoice and InvoiceItem
Invoice, Application and Accommodation all hasMany InvoiceItem
InvoiceItem belongsTo Application, Accommodation and Invoice
The purpose of all this is so that the line items of an Invoice (which come from the InvoiceItem model) can be associated with either an Accommodation or an Application via the InvoiceItem.foreign_id depending on whether InvoiceItem.class is set as Accommodation or Application
From what I understand, this is known as a polymorphic association.
Unfortunately, when I do a $this->Invoice->find('all'); with recursive set to 3 (or set to -1 with the appropriate fields specified in containable) I get this MySQL error:
Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column
'InvoiceItem.class' in 'where clause'
SQL Query: SELECT `Application`.`id`, `Application`.`name`,
`Application`.`created`, `Application`.`updated` FROM `applications`
AS `Application` WHERE `Application`.`id` = 3786 AND
`InvoiceItem`.`class` = 'Application'
I don't understand why Cake would try to add InvoiceItem.class as a condition without creating a join for the InvoiceItem model.
Here are my models (note: I've cut down the number of fields in each for readability -- the Application and Accommodation models share very few similar fields in reality):
Accommodation Model
CREATE TABLE `accommodations` (
`id` int(10) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`created` datetime NOT NULL,
`updated` datetime NOT NULL,
PRIMARY KEY (`id`)
)
<?php
class Accommodation extends AppModel {
var $name = 'Accommodation';
var $hasMany = array(
'InvoiceItem' => array(
'className' => 'InvoiceItem',
'foreignKey' => 'foreign_id',
'conditions' => array('InvoiceItem.class' => 'Accommodation'),
)
);
}
?>
Application Model
CREATE TABLE `applications` (
`id` int(10) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`created` datetime NOT NULL,
`updated` datetime NOT NULL,
PRIMARY KEY (`id`)
)
<?php
class Application extends AppModel {
var $name = 'Application';
var $hasMany = array(
'InvoiceItem' => array(
'className' => 'InvoiceItem',
'foreignKey' => 'foreign_id',
'conditions' => array('InvoiceItem.class' => 'Application'),
)
);
}
?>
InvoiceItem model
CREATE TABLE IF NOT EXISTS `invoice_items` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`class` varchar(30) COLLATE utf8_unicode_ci NOT NULL,
`foreign_id` int(10) unsigned NOT NULL,
`name` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`created` datetime DEFAULT NULL,
`modified` datetime DEFAULT NULL,
PRIMARY KEY (`id`)
)
<?php
class InvoiceItem extends AppModel {
var $name = 'InvoiceItem';
var $belongsTo = array(
'Accommodation' => array(
'foreignKey' => 'foreign_id',
'conditions' => array('InvoiceItem.class' => 'Accommodation')
),
'Application' => array(
'foreignKey' => 'foreign_id',
'conditions' => array('InvoiceItem.class' => 'Application')
),
'Invoice' => array(
'className' => 'Invoice',
'foreignKey' => 'invoice_id',
),
);
}
?>
Invoice model
CREATE TABLE IF NOT EXISTS `invoices` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(100) COLLATE utf8_unicode_ci NOT NULL,
`created` datetime DEFAULT NULL,
`modified` datetime DEFAULT NULL,
PRIMARY KEY (`id`)
)
<?php
class Invoice extends AppModel {
var $name = 'Invoice';
var $hasMany = array(
'InvoiceItem' => array(
'className' => 'InvoiceItem'
'foreignKey' => 'invoice_id'
)
);
}
?>
I'm using CakePHP 2.4.0

Answer 1

class InvoiceItem extends AppModel,and bind no belongsTo.
class InvoiceItem extends AppModel {
var $name = 'InvoiceItem';
var $belongsTo = null
}
you can assign a suitable belongsTo to InvoiceItem at Runtime depend on content
$this->InvoiceItem->bindModel(array( 'belongsTo' => array(...) ) )