RustでErlangVM上で動作するWebアプリケーションを開発する

$ mix phx.new rust_phx_sample --no-ecto

$ mix phx.server

defmodule RustPhxSampleWeb.SampleController do
  use RustPhxSampleWeb, :controller

  def sample(conn, _params) do
    num = add(1, 2)

    render(conn, "sample.json", number: num)
  end

  def add(num1, num2) do
    num1 + num2
  end
end

defmodule RustPhxSampleWeb.SampleView do
  use RustPhxSampleWeb, :view

  def render("sample.json", %{number: num}) do
    %{number: num}
  end
end

  scope "/", RustPhxSampleWeb do
    pipe_through :browser

    get "/", PageController, :index
    get "/sample", SampleController, :sample
  end

  defp deps do
    [
      {:phoenix, "~> 1.5.6"},
      {:phoenix_html, "~> 2.11"},
      {:phoenix_live_reload, "~> 1.2", only: :dev},
      {:phoenix_live_dashboard, "~> 0.3 or ~> 0.2.9"},
      {:telemetry_metrics, "~> 0.4"},
      {:telemetry_poller, "~> 0.4"},
      {:gettext, "~> 0.11"},
      {:jason, "~> 1.0"},
      {:plug_cowboy, "~> 2.0"},
      {:rustler, "~> 0.21.0"} #add
    ]
  end

$ mix deps.get

$ mix rustler.new
This is the name of the Elixir module the NIF module will be registered to.
Module name > RustPhxSampleWeb.SampleController 
This is the name used for the generated Rust crate. The default is most likely fine.
Library name (rustphxsampleweb_samplecontroller) > 
* creating native/rustphxsampleweb_samplecontroller/.cargo/config
* creating native/rustphxsampleweb_samplecontroller/README.md
* creating native/rustphxsampleweb_samplecontroller/Cargo.toml
* creating native/rustphxsampleweb_samplecontroller/src/lib.rs
Ready to go! See /Users/kenseinakada/workspace/rust_phx_sample/native/rustphxsampleweb_samplecontroller/README.md for further instructions.

use rustler::{Encoder, Env, Error, Term};

mod atoms {
    rustler_atoms! {
        atom ok;
        //atom error;
        //atom __true__ = "true";
        //atom __false__ = "false";
    }
}

rustler::rustler_export_nifs! {
    "Elixir.RustPhxSampleWeb.SampleController",
    [
        ("add", 2, add)
    ],
    None
}

fn add<'a>(env: Env<'a>, args: &[Term<'a>]) -> Result<Term<'a>, Error> {
    let num1: i64 = args[0].decode()?;
    let num2: i64 = args[1].decode()?;

    Ok((atoms::ok(), num1 + num2).encode(env))
}

use rustler::{Encoder, Env, Error, Term};

rustler::rustler_export_nifs! {
    "Elixir.RustPhxSampleWeb.SampleController",
    [
        ("add", 2, add)
    ],
    None
}

fn add<'a>(env: Env<'a>, args: &[Term<'a>]) -> Result<Term<'a>, Error> {
    let num1: i64 = args[0].decode()?;
    let num2: i64 = args[1].decode()?;

    Ok((num1 + num2).encode(env))
}

defmodule RustPhxSampleWeb.SampleController do
  use RustPhxSampleWeb, :controller
  use Rustler, otp_app: :rust_phx_sample, crate: :rustphxsampleweb_samplecontroller

  def sample(conn, _params) do
    num = add(1, 2)

    render(conn, "sample.json", number: num)
  end

  def add(_a, _b), do: exit(:nif_not_loaded)
end

  def project do
    [
      app: :rust_phx_sample,
      version: "0.1.0",
      elixir: "~> 1.7",
      elixirc_paths: elixirc_paths(Mix.env()),
      compilers: [:phoenix, :gettext, :rustler] ++ Mix.compilers(), #rustlerの追加
      rustler_crates: rustler_crates(), #追加
      start_permanent: Mix.env() == :prod,
      aliases: aliases(),
      deps: deps()
    ]
  end

  defp rustler_crates() do
    [rustphxsampleweb_samplecontroller: [
      path: "native/rustphxsampleweb_samplecontroller",
      mode: rustc_mode(Mix.env)
    ]]
  end

  defp rustc_mode(:prod), do: :release
  defp rustc_mode(_), do: :debug

$ mix phx.server

defmodule RustPhxSampleWeb.UserController do
  use RustPhxSampleWeb, :controller
  use Rustler, otp_app: :rust_phx_sample, crate: :rustphxsampleweb_usercontroller

  def create(conn, %{"user" => %{"name" => name, "age" => age}}) do
    {:ok, {id, name, age}} = create_user(name, age)

    user = %{
      id: id,
      name: name,
      age: age,
    }

    render(conn, "user.json", user: user)
  end

  def create_user(_name, _age), do: exit(:nif_not_loaded)
end

defmodule RustPhxSampleWeb.UserView do
  use RustPhxSampleWeb, :view

  def render("user.json", %{user: user}) do
    %{user: user}
  end
end

  pipeline :browser do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_flash
    # plug :protect_from_forgery  # セキュリティ上ものすごく良くないがCSRFToken Errorを回避するのがめんどくさいので今回は無効化
    plug :put_secure_browser_headers
  end

#..(中略)
    post "/user", UserController, :create

$ mix rustler.new
This is the name of the Elixir module the NIF module will be registered to.
Module name > RustPhxSampleWeb.UserController
This is the name used for the generated Rust crate. The default is most likely fine.
Library name (rustphxsampleweb_usercontroller) >
* creating native/rustphxsampleweb_usercontroller/.cargo/config
* creating native/rustphxsampleweb_usercontroller/README.md
* creating native/rustphxsampleweb_usercontroller/Cargo.toml
* creating native/rustphxsampleweb_usercontroller/src/lib.rs
Ready to go! See /Users/kenseinakada/workspace/rust_phx_sample/native/rustphxsampleweb_usercontroller/README.md for further instructions.

  defp rustler_crates() do
    [rustphxsampleweb_samplecontroller: [
      path: "native/rustphxsampleweb_samplecontroller",
      mode: rustc_mode(Mix.env)
    ],
    rustphxsampleweb_usercontroller: [                   # add
      path: "native/rustphxsampleweb_usercontroller",
      mode: rustc_mode(Mix.env)
    ]
    ]
  end

$ curl -X POST  -H "Content-Type: application/json" -d '{"user":{"name":"taro", "age":14}}' localhost:4000/user
{"user":{"age":1,"id":1,"name":"taro"}}

$ curl -X POST  -H "Content-Type: application/json" -d '{"user":{"name":"miho", "age":12}}' localhost:4000/user
{"user":{"age":1,"id":2,"name":"miho"}}

diesel_demo=> select * from users;
 id | name | age
----+------+-----
  1 | taro |   14
  2 | miho |   12
(2 rows)