src/Api/Serializer/AbstractSerializer.php
public function hasOne($model, $serializer, $relation = null)
    {
        return $this->buildRelationship($model, $serializer, $relation);
    }
public function hasOne($model, $serializer, $relation = null)
    {
        return $this->buildRelationship($model, $serializer, $relation);
    }
public function hasOne ( $ model , $ serializer , $ relation = null ) { return $ this -> buildRelationship ( $ model , $ serializer , $ relation ) ; }
Get a relationship builder for a has-one relationship.

@param mixed $model
@param string|Closure|\Tobscure\JsonApi\SerializerInterface $serializer
@param string|Closure|null $relation
@return Relationship
Get a relationship builder for a has - one relationship .