How can I have one field updating/changing another one?

Question

I'd like to get fields resolved by another field.

I have a list generated according to some arguments and would like to update the total field

My approach is probably incorrect.

Obviously, I'm trying to avoid re-running the same database query and passing filter up a level in the query string.

So assume the following ruby type for my query:

Types::PostListType = GraphQL::ObjectType.define do
    name 'PostList'

    field :total, !types.Int, default_value: 0 # <-- this is what I'd like to update in :posts resolution
    field :page, !types.Int, default_value: 0 # <-- this is what I'd like to update in :posts resolution
    field :per_page, !types.Int, default_value: 0 # <-- this is what I'd like to update in :posts resolution

    field :posts, types[Types::PostType] do
        argument :page, types.Int, default_value: 1
        argument :per_page, types.Int, default_value: 10 # <-- also need a limit here (hence why I need a field to tell what's been used in the end)
        argument :filter, types.String, default_value: ''
        resolve ->(user, *_args) {
            posts = function_to_filter(args[:filter])
            # how do I update total with posts.count here?
            posts.paginate(page: args[:page], per_page: args[:per_page])
            # how do I update per_page and page?
        }
    end

end

My query is something like this:

query ProspectList {
  posts(filter:"example", page: 2) {
    total
    page
    per_page
    posts {
      id
      ...
    }
  }
}

Answer 1

What you want is returning posts with total, page, per_page without re-running database query.

I'd like to modify query definition, because posts, total, page, per_page should be combined in type.

like this: Types::PostListType

Types::PostListType = GraphQL::ObjectType.define do
  name 'PostList'

  field :total, !types.Int
  field :page, !types.Int
  field :per_page, !types.Int
  field :posts, types[Types::PostType]
end

Then return object in resolve which contains posts, total, page, per_page

Types::QueryType = GraphQL::ObjectType.define do
  name "Query"

  field :postlist, Types::PostListType do
    argument :page, types.Int, default_value: 1
    argument :per_page, types.Int, default_value: 1
    argument :filter, types.String
    resolve ->(_obj, args, _ctx) {
      result = Post.paginate(page: args[:page], per_page: args[:per_page])
      Posts = Struct.new(:posts, :page, :per_page, :total)
      Posts.new(
        result,
        args[:page],
        args[:per_page],
        result.total_entries
      )
    }
  end
end

---

It's also possible define an object and return. Wrapper::PostList

module Wrapper
  class PostList
    attr_accessor :posts, :total, :page, :per_page
    def initialize(posts, page, per_page)
      @posts = posts
      @total = posts.total_entries
      @page = page
      @per_page = per_page
    end
  end
end

...
  field :postlist, Types::PostListType do
    argument :page, types.Int, default_value: 1
    argument :per_page, types.Int, default_value: 1
    argument :filter, types.String
    resolve ->(_obj, args, _ctx) {
      Wrapper::PostList.new(Post.paginate(page: args[:page], per_page: args[:per_page]), args[:page], args[:per_page])
    }
...