feymartynov

class Infix:
    def __init__(self, function):
        self.function = function
    def __rxor__(self, other):
        return Infix(lambda x, self=self, other=other: self.function(other, x))
    def __xor__(self, other):
        return self.function(other)
    def __call__(self, value1, value2):
        return self.function(value1, value2)

feymartynov

# https://medium.com/learn-elixir/disassemble-elixir-code-1bca5fe15dd1

f = './_build/dev/lib/test/ebin/Elixir.Test.beam'
result = :beam_lib.chunks(f,[:abstract_code])
{:ok,{_,[{:abstract_code,{_,ac}}]}} = result
IO.puts :erl_prettypr.format(:erl_syntax.form_list(ac))

feymartynov

defmodule MyApp.Report do
  @report_sql "SELECT * FROM …" # your raw SQL query here

  def with_stream(callback) do
    MyApp.Repo.transaction(fn ->
      stream = Ecto.Adapters.SQL.stream(MyApp.Repo, @report_sql, [])
      callback.(stream)
    end)
  end
end

feymartynov

defmodule MyApp.Report do
  import Ecto.Query

  def with_stream(callback) do
    MyApp.Repo.transaction(fn ->
      query = from MyApp.SomeSchema |> where(…) # your Ecto.Query here
      stream = MyApp.Repo.stream(query)
      callback.(stream)
    end)
  end

feymartynov

defmodule MyApp.ReportController do
  use MyAppWeb, :controller

  def index(conn, _params) do
    conn =
      conn
      |> put_resp_content_type("text/csv")
      |> put_resp_header("content-disposition", ~s[attachment; filename="report.csv"])
      |> send_chunked(:ok)

feymartynov

def authorize(operation, txn_key, action, opts \\ []) do
  user = opts[:user] || operation.context.user

  ExOperation.Operation.step(operation, {:authorize, txn_key}, fn
    %{^txn_key => struct} ->
      policy = (opts[:policy] || struct.__struct__) |> Module.concat(Policy)

      with :ok <- Bodyguard.authorize(policy, action, user, struct: struct) do
        {:ok, :authorized}
      end

feymartynov

# mix.exs
{:ex_operation, “~> 0.4”}

# config/config.exs
config :ex_operation, repo: MyApp.Repo

# lib/myapp/operation.ex
defmodule MyApp.Operation do
  defmacro __using__(opts) do
    quote do

feymartynov

operation
|> step(:foo, &foo/1)
|> defer(fn op, txn ->
  case txn.foo.some_property do
    :one ->
      op |> step(:bar, &bar/1)

    :two ->
      op |> step(:baz, &baz/1)
  end

feymartynov

operation
|> step(:foo, &foo/1)
|> after_commit(fn txn ->
  run_some_async_job(txn.foo)
end)

feymartynov

operation
|> step(:foo, &foo/1)
|> suboperation(OtherOperation, &%{foo_id: &1.foo.id}, id: :sub)
|> step(:bar, &{:ok, &1.sub.result})