How to populate additive field via JOIN with Doctrine - php

Question

Suppose i have an entity with a ManyToOne relation (with EXTRA_LAZY) and obviously a join column.
eg. Article (main entity) -> Author (external entity)
suppose i add a field author_name to the Article that NOT mapped to the ORM and that in certain contexts this field should contain the article->author->name value (usually it can stay null).
When i query a list of articles, i would like to populate automatically that article-author_name without implementing a getter that perform a select on each element of the query result. I would like Doctrine to fetch and hydrate that value in with a simple JOIN in the original query...
I don't want to set fetch mode to EAGER for performance as in my project Author is a really complex entity.
Is this possible?
Thanks

Answer 1

Probably i've found a solution. Don't know if it is the best way to do it but it works.
I've added to the main class a field getter
public getAuthorName() {
return $this->author->name
}
in my context this getter will only be called by a serializer in certain conditions.
In my repository code i have a special method (that i refactored so that any method could implicitly call it) to impose the population of the Article->author field when queried. The method simply use the querybuilder to add LEFT JOIN to the Author class and temporarily set FetchMode to EAGER on Article->author.
At the end a simple repository method could be this
public findAllWithCustomHydration() {
$qb = $this->createQueryBuilder('obj');
$qb->leftJoin("obj.author", "a")
-> addSelect("a"); //add a left join and a select so the query automatically retrive all needed values to populate Article and Author entities
//you can chain left join for nested entities like the following
//->leftJoin("a.address", "a_address")
//-> addSelect("a_address");
$q = $qb->getQuery()
->setFetchMode(Article::class, "author", ClassMetadata::FETCH_EAGER);
//setFetchMode + EAGER tells Doctrine to prepopulate the entites NOW and not when the getter of $article->author is called.
//I don't think that line is strictly required because Doctrine could populate it at later time from the same query result or maybe doctrine automatically set the field as EAGER fetch when a LEFT JOIN is included in the query, but i've not yet tested my code without this line.
return $q->getResult();
}
The con is that you have to customize each query or better use a DQL / SQL / QueryBuilder for each method of the repo but with a good refactoring, for simple inclusion cases, you can write a generic method that inject that join on a field_name array basis.
Hope this help and add your answer if you find a better way.
PS. i've wrote the above code on the fly because now i'm not on my notebook, hope it works at first execution.