Craft GraphQL APIs in Elixir with Absinthe (Pragprog)

@dustin The book is a bit dated but the concepts still work today. Next, I went through the book a bit differently by creating a new Phoenix application using a current version of Phoenix and Elixir. Then I just manually typed most and/or copied and pasted the code from the downloadable source. When I got stuck, I just referenced the Absinthe online documentation. Well, I wish that it helps and all the best to you.

It’s 2024 and it appears that the downloadable code resources are out of date. I just bought the book a few days ago. I get a number of warnings, and the a compilation failure in lib/plate_slate_web/views/layout_view.ex.

Is there a version I might be missing, or any intention on updating the code?

To answer my own question, today I started chapter 9 and it does exactly this thing with a “bookended” middleware using :start and :finish calls. So anyone else doing this, keep reading and all will become clear.

To elaborate, I just expanded the Debug middleware from chapter 9 like this:

defmodule PlateSlateWeb.Schema.Middleware.Debug do
  @behaviour Absinthe.Middleware

  def call(resolution, :start) do
    path = resolution |> Absinthe.Resolution.path |> Enum.join(".")
    time1 = :erlang.timestamp
    IO.puts """
    ========START==========
    started: #{path}
    with source: #{inspect resolution.source}
    """
    %{resolution | middleware: resolution.middleware ++ [{__MODULE__, {:finish, path, time1}}]}
  end

  def call(resolution, {:finish, path, time1}) do
    time2 = :erlang.timestamp
    time_taken = :timer.now_diff(time2, time1)
    IO.puts """
    completed: #{path}
    time taken: #{time_taken} microseconds (#{:erlang.float_to_binary(time_taken * 1.0e-6, [{:decimals, 6}])} seconds )
    value: #{inspect resolution.value}
    ========END==========\
    """
    resolution
  end
end

It’s probably not the best solution but it works for me!

Has anyone found a nice way of doing the challenge at the end of chapter 7 (Resolution Middleware)?

I’ve been trying to do it today and I’m getting nowhere. I think I don’t understand where the time taken is meant to be stored? Should it be on the response?

JFYI the challenge is to “Build some middleware that can be used to measure how long it takes to resolve a field”.

I know I’m showing lack of effort here but I can only do Elixir in my spare time (Python/JS dev by day) so any guidance or hints would be greatly appreciated.

I’m excited to read P2 before the start of my next large project!

I just got the P2 version.

Thanks for updating

This is also correct. The main thing that has tripped people up in the past is that they have tried to use the latest Elixir / Erlang without upgrading Absinthe. This leads to compilation errors. If however you upgrade Absinthe and other dependencies, it should all be smooth sailing.

So what versions of Erlang and Elixir should I use?

I’ve reread the book recently and worked through the examples with elixir 1.8.1 and latest absinthe, dataloader, phoenix, ecto, etc. Don’t remember encountering any major problems, so I’d say the latest versions of everything should work.

Thanks for using Absinthe!

Thank you for your time!