Integrating with ExMachina

Copy Markdown View Source

ExMachina is a popular library for generating data in Elixir. Blink works seamlessly with ExMachina, allowing you to combine ExMachina's expressive factories with Blink's bulk insertion.

Setting up ExMachina

Add ExMachina to your dependencies in mix.exs:

defp deps do
  [
    {:ex_machina, "~> 2.7", only: [:dev, :test]}
  ]
end

Install the dependencies:

mix deps.get

Creating factories

Create a factory module:

defmodule Blog.Factory do
  use ExMachina

  def user_factory do
    %{
      name: Faker.Person.name(),
      email: Faker.Internet.email()
    }
  end

  def post_factory do
    %{
      title: Faker.Lorem.sentence(),
      body: Faker.Lorem.paragraph()
    }
  end
end

Note: To use Faker, add {:faker, "~> 0.18", only: [:dev, :test]} to your dependencies.

Basic integration

Use ExMachina's build/1 function in your Blink seeder:

defmodule Blog.Seeder do
  use Blink
  import Blog.Factory

  def call do
    new()
    |> with_table("users")
    |> run(Blog.Repo)
  end

  def table(_seeder, "users") do
    for _ <- 1..1000 do
      user = build(:user)

      Map.merge(user, %{
        id: Ecto.UUID.generate(),
        inserted_at: ~U[2024-01-01 00:00:00Z],
        updated_at: ~U[2024-01-01 00:00:00Z]
      })
    end
  end
end

In this example, ExMachina generates the names and emails, while you control the IDs and timestamps.

Generating the ID with Ecto.UUID.generate/0 rather than letting the database assign one is what makes the value usable straight away — a later table can reference it before anything is inserted, and a uuid primary key has no sequence to reset. See Choosing IDs.

Summary

In this guide, we learned how to:

  • Use ExMachina's build/1 function with Blink seeders

For more information: