class ResourceTypeRelationship

class ResourceTypeRelationship extends ResourceTypeField {
    
    /**
     * The resource type to which this relationships can relate.
     *
     * @var \Drupal\jsonapi\ResourceType\ResourceType[]
     */
    protected $relatableResourceTypes;
    
    /**
     * Establishes the relatable resource types of this field.
     *
     * @param array $resource_types
     *   The array of relatable resource types.
     *
     * @return static
     *   A new instance of the field with the given relatable resource types.
     */
    public function withRelatableResourceTypes(array $resource_types) {
        $relationship = new static($this->internalName, $this->publicName, $this->enabled, $this->hasOne);
        $relationship->relatableResourceTypes = $resource_types;
        return $relationship;
    }
    
    /**
     * Gets the relatable resource types.
     *
     * @return \Drupal\jsonapi\ResourceType\ResourceType[]
     *   The resource type to which this relationships can relate.
     */
    public function getRelatableResourceTypes() {
        if (!isset($this->relatableResourceTypes)) {
            throw new \LogicException("withRelatableResourceTypes() must be called before getting relatable resource types.");
        }
        return $this->relatableResourceTypes;
    }
    
    /**
     * {@inheritdoc}
     */
    public function withPublicName($public_name) {
        $relationship = parent::withPublicName($public_name);
        return isset($this->relatableResourceTypes) ? $relationship->withRelatableResourceTypes($this->relatableResourceTypes) : $relationship;
    }
    
    /**
     * {@inheritdoc}
     */
    public function disabled() {
        $relationship = parent::disabled();
        return isset($this->relatableResourceTypes) ? $relationship->withRelatableResourceTypes($this->relatableResourceTypes) : $relationship;
    }

}