Constructors & generators composition

[dcebotarenco]

Hello, I am curious if we can do something like this:
Given JPA bidirectional link via a constructor

class Author {
  String name;
  Address address;
  List<Book> books = new ArrayList(); //

  static Author of(String name, Address address) {
    //my internal assignments
   return new Author().setName(name).setAddress(address);
  }
}

class Book {
 Author author;

 public Book(Author author) {
  author.getBooks().add(this); //bidirectional link as part of the constructor
   //my OTHER constructor internal assignments
  this.author = author;
 }

}

A book should always have an author.
The author can have many books.
The book and author have to be bidirectional linked.
Constructor of the Book has to be called

I have a Generator for the Author. Now, I want to have my generator to use my static factories and constructors to make objects in a valid state. I don't want to copy internal assignments as part of the Model I'd have to maintain in both places.
In my case
when I create a Book I want to assign an author.
when I create an Author I want to assign the some books via the constructor of the Books

Generator<Author> authorGenerator = (gen) -> {
    return Author.of("myName", new Address());
};

Generator<Book> bookGenerator = (gen) -> {
    return new Book(????); //can I reference the author other than extracting as a variable and share it between generators
};

I was thinking of reusing the generators

Generator<Book> bookGenerator = (gen) -> {
    Author author = authorGenerator.generate(get);
    return new Book(author);
};

but then the references are different

                Instancio.of(Author.class)
                .supply(root(), authorGenerator)
                .supply(types().of(Books.class), bookGenerator)
                .generate(field(Author::getBooks), gen -> gen.collection().size(1))
                .withSettings(Settings.create()
                        .set(Keys.SET_BACK_REFERENCES, false)
                        .set(Keys.AFTER_GENERATE_HINT, AfterGenerate.POPULATE_NULLS)
                        .set(Keys.OVERWRITE_EXISTING_VALUES, true)
                ).create();

Do I need to create different generators?

• one that fills the graph top-down
• one that fills the graph bottom-up

Do I understand correctly that the idea behind the Instancio is to setup objects bypassing the domain constructors?

[armandino]

@dcebotarenco - Instancio can populate objects via fields or setters. Unfortunately invoking constructors with arguments or static factories is not supported.

Currently, the closest is to use Keys.SET_BACK_REFERENCES, but this will bypass constructors with arguments, which is not what you're looking for.

Author author = Instancio.of(Author.class)
    .withSettings(Settings.create().set(Keys.SET_BACK_REFERENCES, true))
    .create();

I'll need to experiment a bit to see how feasible it is to implement something like this.

[dcebotarenco]

Thanks for looking into it. Appreciate the project!