Vapor: Post processing on a query result?

Question

Vapor/Future newbie here, who's fighting with the type system.

I'd like to do some processing on query results:

1. Do query.
2. Change/save results.
3. Return changed results.

For example:

func myIndex(_ req: Request) throws -> Future<[Todo]> {
    return Todo.query(on: req)
            .all()
            .flatMap { allToDos in
                allToDos.flatMap { toDo in
                    // change toDoch
                    return toDo.save(on: req).flatMap { $0 }
                }
    }
}

Which results in:

So what's the correct pattern for this kind of thing?

Answer 1

Use flatten

func changeAllTodos(_ req: Request) throws -> Future<HTTPStatus> {
    return Todo.query(on: req).all().flatMap { allToDos in
        return allToDos.map { toDo in
            // change toDoch
            return toDo.save(on: req).transform(to: ())
        }.flatten(on: req).transform(to: .ok)
    }
}