Revision: Thu, 25 Apr 2024 11:06:45 GMT

Morphed Relations

Cycle ORM provides support for polymorphic relations. Given relations can be used to link an entity to multiple entity types and select the desired object in runtime. Relations must be assigned to the entity interface rather than a specific role or class name.

In some cases, you might want to associate your entity with any of the external entities which support the given type. This can be achieved using polymorphed relations associated with the entity interface. Such an approach is supported for the hasOne, hasMany and belongsTo relations.

Relations points to the external entity using a complex key [role, outerKey].

Avoid using these relations when possible.

Definition

In order to associate an entity with one of the multiple external objects you have to define a common interface first:

php
use Cycle\Annotated\Annotation\Entity;

#[Entity]
class User implements ImageHolderInterface
{
    // ...
}

#[Entity]
class Post implements ImageHolderInterface
{
    // ...
}

Now we can declare our entity to point to one of the given entities:

php
use Cycle\Annotated\Annotation\Entity;
use Cycle\Annotated\Annotation\Relation\Morphed\BelongsToMorphed;

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

    #[BelongsToMorphed(taget: ImageHolderInterface::class)]
    public ImageHolderInterface $imageHolder;
}

You can use your relation as a standard hasOne after that. Note, eager loading is not possible with belongsToMorphed relation type.

Variations

The ORM provides three basic relations for polymorphic connections:

BelongsToMorphed

BelongsToMorphed relations allows an entity to belong to any of the parents which implement given interface:

Use cases: image attached to (post, user, comment). The relation is similar to belongsTo but does not support eager loading, FKs or select querying. The relation must point to an entity interface.

php
use Cycle\Annotated\Annotation\Entity;
use Cycle\Annotated\Annotation\Relation\Morphed\BelongsToMorphed;

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

    #[BelongsToMorphed(taget: ImageHolderInterface::class)]
    public ImageHolderInterface $imageHolder;
}

Relation options include:

Option Value Comment
load lazy/eager Relation load approach. Defaults to lazy
cascade bool Automatically save related data with source entity. Defaults to true
nullable bool Defines if the relation can be nullable (child can have no parent). Defaults to true
innerKey string Inner key in source entity. Defaults to {relationName}_{outerKey}
outerKey string Outer key in the related entity. Defaults to primary key
morphKey string Name of key to store related entity role. Defaults to {relationName}_role
morphKeyLength int The length of morph key. Defaults to 32
indexCreate bool Create an index on morphKey and innerKey. Defaults to true

MorphedHasOne

MorphedHasOne is an inverse version of BelongsToMorphed.

You can own the entity from multiple entity types (example user/post/comment has an image). The relation must point to an entity role or class.

php
use Cycle\Annotated\Annotation\Entity;
use Cycle\Annotated\Annotation\Relation\Morphed\MorphedHasOne;

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

    #[MorphedHasOne(target: Image::class)]
    public $image;
}

Additional options include:

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}
morphKey string Name of key to store related entity role. Defaults to {relationName}_role
morphKeyLength int The length of morph key. Defaults to 32
indexCreate bool Create an index on morphKey and innerKey. Defaults to true

As in the case with belongsToMorphed, FKs are not supported. You can query or eager load this relation as any other relation types.

MorphedHasMany

MorphedHasMany is an inverse version of BelongsToMorphed.

You can own the entity from multiple entity types (example post/article has comments). The relation must point to an entity role or class.

php
use Cycle\Annotated\Annotation\Entity;
use Cycle\Annotated\Annotation\Relation\Morphed\MorphedHasMany;

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

    #[MorphedHasMany(target: Image::class)]
    public $images;
}

Additional options include:

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}
where array Additional where condition to be applied for the relation. Defaults to none.
morphKey string Name of key to store related entity role. Defaults to {relationName}_role
morphKeyLength int The length of morph key. Defaults to 32
indexCreate bool Create an index on morphKey and innerKey. Defaults to true
collection string Collection type that will contain loaded entities. By defaults uses Cycle\ORM\Collection\ArrayCollectionFactory

As in case with belongsToMorphed, FKs are not supported. You can query or eager load this relation as any other relation types.

Please note, given relations would not be able to automatically create FK keys since the ORM is unable to decide which key must be used. Also, eager loading abilities are limited for such relations (join is only possible for morphedHas* relations).

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