How to check if a association is not loaded?

Question

What function can I use to check if a association is already loaded? It would be nice to check if a association is loaded instead of trying to use it and getting Ecto.Association.NotLoaded error.

Answer 1

You can use assoc_loaded?

Reference: https://hexdocs.pm/ecto/Ecto.html#assoc_loaded?/1

Answer 2

Not sure if there's a built-in function to check for this, but you could write your own like this:

defmodule PreloadCheck do
  def is_preloaded(model, assoc) do
    case Map.get(model, assoc) do
      %Ecto.Association.NotLoaded{} -> false
      _ -> true
    end
  end
end

Here assoc would be the atom representing your association name.

Using pattern matching in case allows you to check if your association is loaded or if it's still returning a Ecto.Association.NotLoaded struct.