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Apr 11, 2023
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[VarExporter] Add Hydrator section #17884

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74 changes: 65 additions & 9 deletions components/var_exporter.rst
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Expand Up @@ -95,30 +95,39 @@ file looks like this::
[]
);

Instantiating PHP Classes
-------------------------
Instantiating & Hydrating PHP Classes
-------------------------------------

The other main feature provided by this component is an instantiator which can
create objects and set their properties without calling their constructors or
any other methods::
Instantiator
~~~~~~~~~~~~

This component provides an instantiator, which can create objects and set
their properties without calling their constructors or any other methods::

use Symfony\Component\VarExporter\Instantiator;

// creates an empty instance of Foo
// Creates an empty instance of Foo
$fooObject = Instantiator::instantiate(Foo::class);

// creates a Foo instance and sets one of its properties
// Creates a Foo instance and sets one of its properties
$fooObject = Instantiator::instantiate(Foo::class, ['propertyName' => $propertyValue]);

// creates a Foo instance and sets a private property defined on its parent Bar class
The instantiator also allows you to populate the property of a parent class. Assuming
``Bar`` is the parent class of ``Foo`` and defines a ``privateBarProperty`` attribute::

use Symfony\Component\VarExporter\Instantiator;

// Creates a Foo instance and sets a private property defined on its parent Bar class
$fooObject = Instantiator::instantiate(Foo::class, [], [
Bar::class => ['privateBarProperty' => $propertyValue],
]);

Instances of ``ArrayObject``, ``ArrayIterator`` and ``SplObjectHash`` can be
created by using the special ``"\0"`` property name to define their internal value::

// Creates an SplObjectHash where $info1 is associated with $object1, etc.
use Symfony\Component\VarExporter\Instantiator;

// Creates an SplObjectStorage where $info1 is associated with $object1, etc.
$theObject = Instantiator::instantiate(SplObjectStorage::class, [
"\0" => [$object1, $info1, $object2, $info2...],
]);
Expand All @@ -128,5 +137,52 @@ created by using the special ``"\0"`` property name to define their internal val
"\0" => [$inputArray],
]);

Hydrator
~~~~~~~~

The instantiator assumes the object you want to populate doesn't exist yet.
Somehow, you may want to fill properties of an already existing object. This is
the goal of the :class:`Symfony\\Component\\VarExporter\\Hydrator`. Here is a
basic usage of the hydrator populating a property of an object::

use Symfony\Component\VarExporter\Hydrator;

$object = new Foo();
Hydrator::hydrate($object, ['propertyName' => $propertyValue]);

The hydrator also allows you to populate the property of a parent class. Assuming
``Bar`` is the parent class of ``Foo`` and defines a ``privateBarProperty`` attribute::

use Symfony\Component\VarExporter\Hydrator;

$object = new Foo();
Hydrator::hydrate($object, [], [
Bar::class => ['privateBarProperty' => $propertyValue],
]);

// Alternatively, you can use the special "\0" syntax
Hydrator::hydrate($object, ["\0Bar\0privateBarProperty" => $propertyValue]);

Instances of ``ArrayObject``, ``ArrayIterator`` and ``SplObjectHash`` can be
populated by using the special ``"\0"`` property name to define their internal value::

use Symfony\Component\VarExporter\Hydrator;

// Creates an SplObjectHash where $info1 is associated with $object1, etc.
$storage = new SplObjectStorage();
Hydrator::hydrate($storage, [
"\0" => [$object1, $info1, $object2, $info2...],
]);

// creates an ArrayObject populated with $inputArray
$arrayObject = new ArrayObject();
Hydrator::hydrate($arrayObject, [
"\0" => [$inputArray],
]);

.. versionadded:: 6.2

The :class:`Symfony\\Component\\VarExporter\\Hydrator` was introduced in Symfony 6.2.

.. _`OPcache`: https://www.php.net/opcache
.. _`PSR-2`: https://www.php-fig.org/psr/psr-2/