Revision: Fri, 29 Mar 2024 18:33:18 GMT

Refers To

The RefersTo relation is similar to the BelongsTo relation, but must be used to establish multiple relations to the same entity (or in case of a cyclic relation). The most common example is the ability to store the last comment posted by the user.

The entity will be persisted before the related entity and then updated.

Definition

Using the annotated extension:

php
use Cycle\Annotated\Annotation\Entity;
use Cycle\Annotated\Annotation\Relation\RefersTo;
use Cycle\Annotated\Annotation\Relation\HasMany;

#[Entity]
class User
{
    // ...

    #[RefersTo(target: Comment::class)]
    private ?Comment $lastComment;

    #[HasMany(target: Comment::class)]
    public array $comments;

    // ...

    public function addComment(Comment $c): void
    {
        $this->lastComment = $c;
        $this->comments[] = $c;
    }
    
    public function removeLastComment(): void
    {
        $this->lastComment = null;
    }
    
    public function getLastComment(): ?Comment
    {
        return $this->lastComment;
    }
}

You must properly handle the cases when the relation is not initialized (null)!

By default, the ORM will generate an outer key in the relation object using the related entity's role and outer key ( primary key by default) values. As result column and FK will be added to Post entity on user_id column.

Option Value Comment
load lazy/eager Relation load approach. Defaults to lazy
cascade bool Automatically save related data with parent entity. Defaults to true
nullable bool Defines if the relation can be nullable (child can have no parent). Defaults to false
innerKey string Inner key in parent entity. Defaults to the primary key
outerKey string Outer key name. Defaults to {parentRole}_{innerKey}
fkCreate bool Set to true to automatically create FK on outerKey. Defaults to true
fkAction CASCADE, NO ACTION, SET NULL FK onDelete and onUpdate action. Defaults to SET NULL
fkOnDelete CASCADE, NO ACTION, SET NULL FK onDelete action. It has higher priority than {$fkAction}. Defaults to @see {$fkAction}
indexCreate bool Create an index on outerKey. Defaults to true

Please note, default fkAction is SET NULL, the relation is nullable by default.

Usage

Cycle ORM will automatically save the related entity and link to it (unless cascade set to false).

php
$user = new User();
$user->addComment(new Comment("hello world"));

$manager = new \Cycle\ORM\EntityManager($orm);
$manager->persist($user);
$manager->run();

Simply set the property value to null to remove the entity reference.

php
$user = new User();
$user->removeLastComment();;

$manager = new \Cycle\ORM\EntityManager($orm);
$manager->persist($user);
$manager->run();

Loading

To access related data call the method load of your Post's Select object:

php
$user = $orm->getRepository(User::class)
    ->select()
    ->load('lastComment')
    ->wherePK(1)
    ->fetchOne();

print_r($user->getLastComment());

Filtering

You can filter entity selection using related data, call the method with of your entity's Select to join the related entity table:

php
$users = $orm->getRepository(User::class)
    ->select()
    ->with('lastComment')->where('lastComment.approved', true)
    ->fetchAll();

print_r($users);

Select can automatically join related table on the first where condition. The previous example can be rewritten:

php
$users = $orm->getRepository(User::class)
    ->select()
    ->where('lastComment.approved', true)
    ->fetchAll();

print_r($users);

Self References

The RefersTo relation can be used to create self-references.

php
use Cycle\Annotated\Annotation\Entity;
use Cycle\Annotated\Annotation\Column;
use Cycle\Annotated\Annotation\Relation\RefersTo;

#[Entity]
class Category
{
     #[Column(type: 'primary')]
    public int $id;

     #[RefersTo(target: Category::class)]
    public ?Category $parent;

    // ...
}

To create a tree like that:

php
$category1 = new Category("A");
$category2 = new Category("A");
$category2->parent = $category1;

$manager = new \Cycle\ORM\EntityManager($orm);
$manager->persist($category1);
$manager->persist($category2);
$manager->run();

You can load relations like that on any level (considering memory and performance limitations):

php
$result = $orm->getRepository(Category::class)
    ->select()
    ->load('parent.parent.parent.parent') // load 4 parent levels
    ->fetchAll();

Make sure that cyclic dependencies are what you need.

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