Add save 1:N support for Lookup multiple

[woodholly]

How to reproduce:

1. open /demos/form-control/lookup-dep.php
2. select 2+ countries in bottom (the last) dropdown
3. click save

Result:

Expected result: Submitted: Array ...

[mvorisek]

This is a feature as we must always typecast everything from/to ui.

It is implemented for json DBAL type already in https://github.com/atk4/ui/blob/6.0.0/src/Form/Control/Lookup.php#L157.

But for other types, how to set the value in (single) entity/field?

[mvorisek]

We must not set entityField property for lookup multiple or never use it for values. By definition, the field type must match the value type. We cannot set array of values for non-array type.

The proper solution will be implement 1:N support for form controls and possibly together with https://github.com/atk4/data/blob/develop/src/Reference/ContainsMany.php.

I would need commercial funding to work on this. Contributions welcomed, but quite a lot of code needs to be added.

[woodholly]

I can't reproduce this in non-demo environment. Why this works ?

<?php

use Atk4\Data\Model;
use Atk4\Data\Persistence;
use Atk4\Ui\Form;

/** @var App $app */
require_once __DIR__ . '/../init-app.php';

$form = \Atk4\Ui\Form::addTo($app);

$lookupModel = new Model();
$lookupModel->addField('id', ['type' => 'integer']);
$lookupModel->addField('name', ['type' => 'string']);
$lookupModel->setPersistence(new Persistence\Array_(array_combine(
    range(1,3),
    array_map(static fn ($a) => ['name' => "string$a"], range(1,3))
)));
$lookup = $form->addControl('test', [
    Form\Control\Lookup::class,
    'model' => $lookupModel,
    'multiple' => true,
]);
$form->onSubmit(static function (Form $form) {
    return 'Submitted: ' . print_r($form->entity->get(), true);
});

I probably found 1 new bug - try selecting all 3 values and click save :)

[mvorisek]

The issue is exactly the same. With multiple=true the values are sent like 1,2,3. Try selecting only 2. It will parse the 1,2 number and then cast it to integer.

The issue here is how to store 1:N values in component that work with 1:1 currently only as I described above.

[mkrecek234]

Just a thought - a lot of professional applications use comma-separated text fields to list multiple elements in import/export (e.g., mailchimp, e.g. for tag lists) - even though from a database perspective being 1:N this might not reflect the correct data structure.

However for an agile framework storing comma-separated lists in a text field in the database might often be the most-effectve way - I have many use cases where I don't need database query power in such fields, and thus it is fully sufficient. Storing it in 1 1:N table would make it unnecessarily complex.
I work very effectively with multiple dropdown control fields in many use cases

[mvorisek]

We do as well. I belive when you will set the type to string it will work. But we also very strictly typecast everything and for ex. datetime typecast produce an object in php world. We cannot join objects with comma and the only way is to store them in an array. I am going to close this issue as it is a feature request someone have to back up. Contributions welcomed.

[woodholly]

@mvorisek perhaps this problem does not need to be solved, because the nature of such fields is oneToMany/manyToMany relation.

[mvorisek]

It is as saving the 1:N relation from form field control is currently not possible outside JSON (which is 1:1 at the end).

[woodholly]

So, that means, that there is also no <select multiple> control ?