Cakephp: exposed virtual field are not included in query - mysql

Question

I read some other questions but they are very old. I'm using CakePHP 3.7.9.
I read the documentation about virtual fields, here and here.
So far:
Proforma.php
class Proforma extends Entity
{
protected $_accessible = [
'customer_id' => true,
'proforma_number' => true,
'proforma_date' => true,
'payment_date' => true,
'proforma_state_id' => true,
'customer' => true,
'proforma_state' => true,
'item_proformas' => true
];
protected $_virtual = [
'total'
];
protected function _getTotal()
{
$q = TableRegistry::getTableLocator()->get('item_proformas')->find();
$v = $q
->select(['total' => $q->func()->sum('total')])
->where(['proforma_id' => $this->id])
->first()['total'];
if ($v == null) $v = 0;
return $v;
}
}
In views I can easily access to this field:
<td class="text-right"><?= $proforma->item_proformas ? $this->Number->currency($proforma->total) : '' ?></td>
But when I try to make a query in Controller, i.e.:
$query = $this->Proformas->find();
debug($query);
$query->select(['value' => $query->func()->sum('total')]);
The field total is not found. Here the output of the debug:
object(Cake\ORM\Query) {
'(help)' => 'This is a Query object, to get the results execute or iterate it.',
'sql' => 'SELECT Proformas.id AS `Proformas__id`, Proformas.customer_id AS `Proformas__customer_id`, Proformas.proforma_number AS `Proformas__proforma_number`, Proformas.proforma_date AS `Proformas__proforma_date`, Proformas.payment_date AS `Proformas__payment_date`, Proformas.proforma_state_id AS `Proformas__proforma_state_id` FROM proformas Proformas',
'params' => [],
'defaultTypes' => [
'Proformas__id' => 'integer',
'Proformas.id' => 'integer',
'id' => 'integer',
'Proformas__customer_id' => 'integer',
'Proformas.customer_id' => 'integer',
'customer_id' => 'integer',
'Proformas__proforma_number' => 'string',
'Proformas.proforma_number' => 'string',
'proforma_number' => 'string',
'Proformas__proforma_date' => 'date',
'Proformas.proforma_date' => 'date',
'proforma_date' => 'date',
'Proformas__payment_date' => 'date',
'Proformas.payment_date' => 'date',
'payment_date' => 'date',
'Proformas__proforma_state_id' => 'integer',
'Proformas.proforma_state_id' => 'integer',
'proforma_state_id' => 'integer'
],
'decorators' => (int) 0,
'executed' => false,
'hydrate' => true,
'buffered' => true,
'formatters' => (int) 0,
'mapReducers' => (int) 0,
'contain' => [],
'matching' => [],
'extraOptions' => [],
'repository' => object(App\Model\Table\ProformasTable) {
'registryAlias' => 'Proformas',
'table' => 'proformas',
'alias' => 'Proformas',
'entityClass' => 'App\Model\Entity\Proforma',
'associations' => [
(int) 0 => 'customers',
(int) 1 => 'proformastates',
(int) 2 => 'invoices',
(int) 3 => 'itemproformas'
],
'behaviors' => [],
'defaultConnection' => 'default',
'connectionName' => 'default'
}
}
Why even if the virtual field is exposed it's not inserted into the query?
The documentation linked above says:
Do bear in mind that virtual fields cannot be used in finds. If you want them to be part of JSON or array representations of your entities, see Exposing Virtual Fields.
and then:
By default virtual fields are not exported when converting entities to arrays or JSON. In order to expose virtual fields you need to make them visible. When defining your entity class you can provide a list of virtual field that should be exposed
So exposing virtual fields should let me to use them in finds.

Answer 1

Sadly Virtual fields are not calculated at the point the query is run. Here are some alternative approaches you may find helpful.
Create View of the actual table ( handle the sum at the DB level)
Create A beforeFind event in the table model.