Question, best way to decorate with preloaded relations

[acabreragnz]

Hi all, thank you for the hard work. I have a question.

Suppose that I have a decorated field in the Post schema, but then I do something like

def preload(users_query, preloads) do
   Users
   |> Repo.all()
   |> Repo.preload(preloads)
end

where preloads is dynamic, and could be i.e. [:posts, :comments, :likes, ...]

Which is the correct way to work in cases where you preload the relations, and those relations have decorated fields?

Thank you!

[rsierra]

At the moment, I just can think in decorate each relation by hand. Somethig like this:

def preload(users_query, preloads) do
   users_query
   |> Repo.all()
   |> Repo.preload(preloads)
   |> Enum.map(&decorate_preloads(&1, preloads))
end

defp decorate_preloads(struct, preloads) do
   Enum.reduce(preloads, struct, , fn(preload, struct) -> decorate_preload(struct, preload) end)
end

defp decorate_preload(struct, preload) do
   Map.put(struct, preload, do_decorate_preload(Map.get(preload)))
end

# If the preload is a list, decorate each element
defp do_decorate_preload(preloads) when is_list(preloads) do
  Enum.map(preloads, &do_decorate_preload/1)
end

# If custom decorations are needed
defp do_decorate_preload(%Post{} = post) do
  Decoratex.decorate(post, except: :comments_count)
end

# Default decorations
defp do_decorate_preload(preload) do
  Decoratex.decorate(preload)
end

But you will need more pattern matching and complexity if you use keyword lists for nested preloads.