Usage of ManyToOne relation returns null in TypeGraphQL - node.js

Question

For learning, I made a project testing out TypeGraphql, together with TypeORM. I have a User and Book entity, where I want to have a created_by field on the Book entity.
#ObjectType()
#Entity()
export class Book extends BaseEntity {
#Field(() => ID)
#PrimaryGeneratedColumn()
readonly id: number;
#Field({ nullable: true })
#Column({ nullable: true })
name: string;
#Field(() => User)
#ManyToOne(() => User)
#JoinColumn({ name: 'created_by' })
created_by: User;
// #RelationId((orthodontist: Orthodontist) => orthodontist.created_by)
// createdById: number;
}
#ObjectType()
#Entity()
export class User extends BaseEntity {
#Field(() => ID)
#PrimaryGeneratedColumn()
id: number;
#Field({ nullable: true })
#Column({ nullable: true })
first_name?: string;
#Field({ nullable: true })
#Column({ nullable: true })
last_name?: string;
#Field()
#Column({ unique: true })
email: string;
#Column()
password: string;
#Field(() => [Book!])
#OneToMany(() => Book, book => book.created_by)
created_books: Book[];
}
For my resolver, it simply looks like this, which I am properly loading as the docs say.
#Resolver(Book)
export class OrthodontistResolver {
#Query(() => [Book])
books(): Promise<Book[]> {
return Book.find();
}
}
When I go into my GraphQL playground, and query something like this:
{
books {
name,
id,
}
}
It all works and returns the right data. However, when I try to use the created_by field like this:
{
orthodontists {
name,
id,
created_by {
id
}
}
}
It gives me the following error:
Cannot return null for non-nullable field Book.created_by.
I made sure the relation exists in the database, and set up correctly with it's FK's. Where does this come from though? How can I fix this? I did try using the #RelationId decorator, as seen in the first code example. It unfortunately didn't work.
EDIT:
There is only one book in the database, where the created_by field is not null.

Answer 1

Change your books resolver to return the relationship created_by when using find operation:
#Resolver(Book)
export class OrthodontistResolver {
#Query(() => [Book])
books(): Promise<Book[]> {
return Book.find({
relations: ["created_by"],
});
}
}