Ecto is an ORM library for Elixir that works without object-oriented concepts like ActiveRecord in Ruby. It uses functions and data structures instead of method calls on objects. Queries return flexible maps instead of objects. Repositories handle database connections and queries can be built with an integrated query language. Models define schemas and changesets handle validation and casting of parameters. Ecto supports features like migrations, multiple repositories, and works with databases like Postgres.

1. @vanstee
operable.io

2. Ectoan ORM without objects

3. Ruby and ActiveRecord
Elixir and Ecto
=

4. ActiveRecord refresher
# Create an unpersisted record
user = User.new(name: "Caroline Holbrook")
# Modify the user
user.name = "Caroline Van Stee"
# Persist a record
user.save
# Retrieve a record
User.find(1)
# Run a complex query
User.where(admin: true).count

5. Calling methods on
objects, that have
methods which
return objects…

6. I love Ruby,
but what if we wanted
to build an ORM
without objects.

7. Data structures Functions
Models
Queries Attribute Mapping
Validations
Executing Queries

8. User.where(name: "Patrick")
query = { table: :users,
where: { name: "Patrick" } }
results = execute(connection, query)
users = results.map(&:to_model)
with objects
without objects

9. Wait, you just turned
1 line into 3.
How could that be
any better?

10. Queries are more flexible1
Connections can be
swapped out
2
Results are more flexible
and are just simple maps
3

11. Well, that's
how Ecto
works!

12. query = from u in User,
where: u.name == "Patrick"
results = Repo.all(query)

13. Integrated
Query
Language

14. Repo
Model
Changeset
Query

15. Repos are just
connections to
the database

16. user = %User{name: "Patrick"}
WriterRepo.insert!(user)
ReaderRepo.all(User)
Multiple Repos

17. Models
defmodule App.User do
use Ecto.Model
schema "users" do
field :name
end
end

18. Fields have types
defmodule JSON do
alias Postgres.TypeInfo
@behaviour Postgrex.Extension
def init(_parameters, opts),
do: Keyword.fetch!(opts, :library)
def matching(_library),
do: [type: "json"]
def format(_library),
do: :binary
def encode(%TypeInfo{type: "json"}, map, _state, library),
do: library.encode!(map)
def decode(%TypeInfo{type: "json"}, json, _state, library),
do: library.decode!(json)
end

19. Changesets
defmodule User do
use Ecto.Model
def changeset(user, params :empty) do
user
|> cast(params, ~w(name email), ~w(age))
|> unique_constraint(:email)
end
end

20. Changesets
params = %{email: "patrick@vanstee.me"}
changeset = User.changeset(%User{}, params)
{:error, changeset} = Repo.insert(changeset)
changeset.errors
#=> [email: "has already been taken"]

21. Queries
from u in User,
join: p in Post, on: u.id == p.user_id,
where: u.name == "Patrick" or p.views > 500,
select: {u.name, p.title}

22. Everything else
• Migrations
• Mix tasks (like rake)
• Callbacks
• Validations
• PostgreSQL, MySQL, Mongo

23. ⚡

24. elixir-lang.org
elixir-lang/ecto