Elixir and Ecto

Transcript

1. elixir
   atlanta
   meetup
   

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2. meetup.com/
   atlantaelixir
   @vanstee
   

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4. • speakers
   • sponsors
   • twitter
   • website
   • github org
   • [your great idea]
   

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5. elixir and ecto
   

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6. Elixir is a functional,
   meta-programming
   aware language built on
   top of the Erlang VM.
   

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7. elixir-lang/elixir
   @josevalim
   

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8. defmodule Hello do
   IO.puts "Before world defined"
   def world do
   IO.puts "Hello World"
   end
   IO.puts "After world defined"
   end
   Hello.world
   HELLO.EX
   

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10. Types
    

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11. # tuple
    { :a, :b, :c }
    # list
    [1, 2, 3]
    [a: 1, b: 2, c: 3]
    # record
    defrecord User, name: "", age: nil
    User.new(name: "Patrick", age: 25)
    TYPE.EX
    

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12. Pattern
    Matching
    

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13. # assignment
    a = 1 # => 1
    # matching
    1 = a # => 1
    2 = a # => ** (MatchError) ...
    { ^a, b } = { 1, 2 } # b => 2
    [head | _] = [1, 2, 3] # head => 1
    PATTERN.EX
    

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14. case { 1, 2, 3 } do
    { 4, 5, 6 } ->
    "This won't match"
    { 1, x, 3 } when x > 0 ->
    "This will match and assign x"
    _ ->
    "No match"
    end
    GUARD.EX
    

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15. Processes
    

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16. current_pid = self
    spawn fn ->
    current_pid <- :hello
    end
    receive do
    :hello ->
    IO.puts "Hello World"
    end
    PROCESS.EX
    

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17. defmodule Stacker.Supervisor do
    use Supervisor.Behaviour
    def start_link(stack) do
    :supervisor.start_link(__MODULE__, stack)
    end
    def init(stack) do
    children = [worker(Stacker.Server, [stack])]
    supervise children, strategy: :one_for_one
    end
    end
    SUPERVISOR.EX
    

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18. Protocols
    Macros
    DocTest
    and lots more
    

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19. elixir-lang.org
    #elixir-lang
    

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22. ecto
    database query DSL
    

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23. elixir-lang/ecto
    @ericmj
    

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24. defmodule User do
    use Ecto.Model
    queryable "user" do
    field :name, :string
    end
    end
    MODEL.EX
    

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25. defmodule FindUser do
    import Ecto.Query
    def find_by_name(name) do
    query = from u in User,
    where: u.name == ^name,
    limit: 1
    Repo.all(query)
    end
    end
    QUERY.EX
    

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27. Repo
    

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28. • wrapper
    • holds connections
    • executes queries
    • supervised worker
    

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29. defmodule Repo do
    use Ecto.Repo,
    adapter: Ecto.Adapters.Postgres
    def url do
    "ecto://user:pass@localhost/db"
    end
    end
    Repo.all(...)
    Repo.create(...)
    Repo.update(...)
    Repo.delete(...)
    REPO.EX
    

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30. Entity
    

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31. • fields
    • associations
    • elixir record
    

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32. defmodule User do
    use Ecto.Model
    queryable "user" do
    field :name, :string
    field :password, :string,
    default: "secret"
    has_many :projects, Project
    end
    end
    MODEL.EX
    

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33. Query
    

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34. • relational algebra
    • extendable
    • macros
    • keyword lists
    

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35. def paginate(query, page, size) do
    extend query,
    limit: size,
    offset: (page - 1) * size
    end
    query = FindUser.find_by_state("GA")
    query |> paginate(1, 50) |> Repo.all
    PAGINATE.EX
    

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36. from u in User,
    where: u.name == ^name,
    limit: 1
    QUERY.EX
    

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37. from(u in User) |>
    where([u], u.name == ^name) |>
    limit(1) |>
    select([u], u)
    QUERY.EX
    

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38. select(
    limit(
    where(
    from(u in User),
    [u], u.name == ^name
    ), 1
    ), [u], u
    )
    QUERY.EX
    

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39. Gotchas
    

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40. • error messages
    • validations
    • callbacks
    • type conversions
    • SQL migrations
    • missing mix tasks
    

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41. elixir-lang/ecto
    examples/simple
    

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42. Thanks!
    @josevalim
    @ericmj
    #elixir-lang
    

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43. ?
    

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