Meta Entity

Meta Entity Description
Meta Entity module allows to add metadata about an entity, stored in a dedicated entity (meta_entity). This is useful when you want to avoid storing this information as a content entity field and clutter the content entity with data that is not part of the content but is metadata (data about other data).

Requirements

* Dynamic Entity Reference module.

How to use it?
Even though the module provides a user interface, it's mainly intended to be used programmatically. Meta data is represented by entities, of type meta_entity that are linking content entities. Meta entity types can be defined as bundle configuration entities (of type meta_entity_type) in order to define types of metadata (e.g. visits count, download count, etc). Each meta_type entity is linked to a content entity (such as node, taxonomy term, etc) via a Dynamic Entity Reference field.

A content entity can be referred by a single meta entity of that type. When defining a meta entity type, the site builder can choose the bundles of content entities that can be linked by that specific type of metadata.

Reverse references
On each bundle selected for a given meta entity bundle, the site builder may configure a field name. The target entity will automatically expose an entity_reference computed field with that name, linking back to the meta entity.

API usage
Create a meta entity type to be used on 'article' nodes:

MetaEntityType::create([ 'id' => 'visits', 'label' => 'Visits', 'mapping' => [ // Node entity type ID. 'node' => [ // The array is keyed by bundle ID. The values are configuration arrays // containing: // - field_name: (optional) A field identifier string may be configured // as value. In this example the 'article' nodes will automatically // expose a field named `visits` which is a reference to the node's // meta entity. // - auto_create: (optional) A boolean value indicating whether to // automatically create a 'visits' meta entity when an 'article' node // is created. 'article' => [ 'field_name' => 'visits', 'auto_create' => TRUE, ], // If the configuration array is empty, no computed field is created and // the no meta entity is created when a 'page' node is created but it's // still allowed to create meta entities for 'page' nodes. 'page' => [], ], // Entity types without bundles, such as 'user', should use the entity type // ID as bundle ID. 'user' => [ 'user' => [ ... ], ], ], ])->save(); Add all needed fields to this meta entity type, either as config entities or using the UI. For instance, in the above example you could add a configurable field field_count of type integer.

Create an 'article' node.

$node = Node::create([ 'type' => 'article', 'title' => 'News From The World', ... ]); $node->save(); Create and link the meta entity:

$visits = MetaEntity::create([ 'type' => 'visits', 'target' => $node, 'field_count' => 10, ]); $visits->save(); Now the node $node has metadata, represented by a meta entity of type visits, associated without the node to be touched. The meta entity can update (e.g. increment the field_count) without needing to re-save the $node. On meta entity update, also the $node cache tags are invalidated.

The content entity can refer directly the meta entity, via the computed reverse reference:

$message = t('@count visits', [ '@count' => $node->visits->entity->field_count->value; ]); For this reason, creating an entity with its meta entity could be achieved in a single step:

Node::create([ 'type' => 'article', 'title' => 'News From The World', 'visits' => MetaEntity::create([ 'type' => 'visits', 'field_count' => 10, ]), ])->save(); Supposing a new meta entity type downloads is added and a new metadata entity of this type is linked to $node:

MetaEntityType::create([ 'id' => 'downloads', 'label' => 'Downloads', 'mapping' => [ 'node' => [ 'article' => [ 'field_name' => 'download_count', ], ], ], ])->save(); $downloads = MetaEntity::create([ 'type' => 'downloads', 'target' => $node, 'field_count' => 100, ]); $downloads->save(); Now there are two reverse reference fields exposed on the node:

// Will return $downloads. $node->download_count->entity; // Will return $visits. $node->visits->entity;