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def wait_until(timeout \\ 1_000, fun)

def wait_until(0, fun), do: fun.()

def wait_until(timeout, fun) do
  fun.()
rescue
  ExUnit.AssertionError ->
    :timer.sleep(10)

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const Hooks = { ViewportResizeHooks}

const connectLiveSocket = () => {
  const csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute('content')
  const liveSocket = new LiveSocket('/my_app/live', Socket, {
    params: {
      _csrf_token: csrfToken,
      viewport: {
        width: window.innerWidth,
        height: window.innerHeight

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Architecture principles

From Design It! From Programmer to Software Architect by Michael Keeling.

• Partition system and assign responsibilities.
• Decide trade-offs among quality attributes:
  • Performance (response time)
  • Scalability (annual growth)
  • Availability
  • Security

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defmodule Projections.Repo.Migrations.CreateProjectionVersions do
  use Ecto.Migration

  def change do
    create table(:projection_versions, primary_key: false) do
      add :projection_name, :text, primary_key: true
      add :last_seen_event_id, :bigint

      timestamps
    end

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defmodule UniqueUsername do
  @behaviour Commanded.Middleware

  alias Commanded.Middleware.Pipeline
  
  def before_dispatch(%Pipeline{command: %RegisterUser{} = command} = pipeline) do
    %RegisterUser{username: username} = command

    case Repo.insert(%Username{username: username}) do
      {:ok, _} -> 

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Elixir tips

Editor

• Atom editor.
• atom-elixir package.

Style guide

• The Elixir style guide.

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Commanded middleware for command enrichment

Usage

Add the EnrichCommand middleware to your command router:

defmodule MyApp.Router do
  use Commanded.Commands.Router
 

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Big-O Time Complexities for Elixir data structures

Map [1]

Operation	Time Complexity
Access	O(log n)
Search	O(log n)
Insertion	O(n) for < 32 elements, O(log n) for >= 32 elements [2]
Deletion	O(n) for < 32 elements, O(log n) for >= 32 elements

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docker pull postgres:12-alpine

docker run --rm \
  --name postgres10 \
  --tmpfs=/pgtmpfs \
  -e PGDATA=/pgtmpfs \
  -e POSTGRES_PASSWORD=postgres \
  -e POSTGRES_USER=postgres \
  -p 5432:5432 \
  postgres:10-alpine

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defmodule EventStore.CategoryStreamLinker do
  @moduledoc """
    Links streams from aggregate instances to their respective category streams.

    example: events from stream_uuid of `contractors_contract-07c52787-da0c-444f-9783-5d380f7093f9` will be
    linked to stream_uuid of `contractors_contract`.
  """

  use Commanded.Event.Handler,
    application: My.App,