src/Eloquent/AbstractAdapter.php
protected function fillRelated(
        $record,
        ResourceObject $resource,
        EncodingParametersInterface $parameters
    ) {
        $relationships = $resource->getRelationships();
        $changed = false;

        foreach ($relationships as $field => $value) {
            /** Skip any fields that are not fillable. */
            if ($this->isNotFillable($field, $record)) {
                continue;
            }

            /** Skip any fields that are not relations */
            if (!$this->isRelation($field)) {
                continue;
            }

            $relation = $this->getRelated($field);

            if ($this->requiresPrimaryRecordPersistence($relation)) {
                $relation->update($record, $value, $parameters);
                $changed = true;
            }
        }

        /** If there are changes, we need to refresh the model in-case the relationship has been cached. */
        if ($changed) {
            $record->refresh();
        }
    }
protected function fillRelated(
        $record,
        ResourceObject $resource,
        EncodingParametersInterface $parameters
    ) {
        $relationships = $resource->getRelationships();
        $changed = false;

        foreach ($relationships as $field => $value) {
            /** Skip any fields that are not fillable. */
            if ($this->isNotFillable($field, $record)) {
                continue;
            }

            /** Skip any fields that are not relations */
            if (!$this->isRelation($field)) {
                continue;
            }

            $relation = $this->getRelated($field);

            if ($this->requiresPrimaryRecordPersistence($relation)) {
                $relation->update($record, $value, $parameters);
                $changed = true;
            }
        }

        /** If there are changes, we need to refresh the model in-case the relationship has been cached. */
        if ($changed) {
            $record->refresh();
        }
    }
Hydrate related models after the primary record has been persisted.

@param Model $record
@param ResourceObject $resource
@param EncodingParametersInterface $parameters