how to set many-to-many relation in graphql mutation?

Question

I may be missing something, but can not find any information on Apollo docs about the way to set a many-to-many relation when creating a new entry.

When the relation is one-to-many it is as simple as setting the ID of the one-side of the relationship in the many-side object.

But let's pretend I am working with Books and Authors, how would I write a graphql query that creates a Book for one (or many?) Authors?

Solution

This should probably happen at the API layer on the GraphQL server (i.e. schema). For many-to-many relationships, you should have a "join" type to denote the BookAuthor many-to-many relationship, and then add an entry to that join type.

Essentially then you'll have a type called Book, another called Author, and finally one more called BookAuthor. And you can add a few mutations to be able to manage that relationship. Perhaps...

• addToBookAuthorConnection
• updateBookAuthorConnection
• removeFromBookAuthorConnection

This is a conventional setup using a Relay-spec compliant API. You can read more about how to structure your API for many-to-many relationships here.

Then, you only need to call the addToBookAuthorConnection mutation from Apollo instead to be able to add to that many-to-many connection on your frontend.

Hope this helps!