elixir-tips-tricks

Just random tips and tricks while working with elixir [& phoenix and other libs/frameworks]

Disable compiling of dependency in mix

{:my_dep, …, compile: false}

Run only particular tests

Use @tag :wip in the test you want to run

defmodule MyTest do
  use ExUnit.Case
  
  test "first test" do
    assert 1 == 1
  end
  
  @tag :wip
  test "second test" do
    assert 3 != 5
  end
end

mix test --only wip

Build composable queries with Inquisitor

Check the Inquisitor repository if you're looking for building composable queries for Ecto.

iex shortcuts

• c "somefile.exs" - compile the file
• r SomeModule - reload the module
• h some_func - get help for the function
• v [n] - access session history

Get query and post params excluding others in params (phoenix)

conn.body_params # gives params from POST
conn.query_params # query string parameters

Run multiple mix tasks

MIX_ENV=test mix do deps.get, test

Update particular dependency

mix deps.update <dep_name>

Turn off layout on Phoenix.Controller.render/3

render conn, "index.html", %{layout: false}
# with plug
plug :put_layout, false

# pipe it
conn |> put_layout(false) |> render(...)

Increase stacktrace

:erlang.system_flag(:backtrace_depth, 20)

# with phoenix
# config/env.exs
config :phoenix, :stacktrace_depth, 20

Observer on remote erlang node

$ iex --name [email protected] --cookie iam_not_so_awesome -S mix phoenix.server  # in api server

# on separate shell
$ iex --name [email protected] --remsh [email protected] --cookie iam_not_so_awesome
iex([email protected])1> :observer.start

You can pass args down to erlang via erl flag. Example: --erl "-kernel inet_dist_listen_min 9001 inet_dist_listen_m 9001"

Change default compile output directory

Based on this, you can specify a keyword list arg build_path to override the default _build directory.

Example:

def project do
    [app: :my_app,
    version: "0.0.1",
    elixir: "~> 1.2",
    build_embedded: Mix.env == :prod,
    start_permanent: Mix.env == :prod,
    build_path: "custom_build_dir",
    deps: deps]
end

Emmet tab support for eex in Atom

Open your preferences and select keymaps. It should open keymaps.cson. Add the following in that file:

'atom-text-editor[data-grammar="text html elixir"]:not([mini])':
    'tab': 'emmet:expand-abbreviation-with-tab'

The grammar can be obtained for any files by opening console (ctrl+shift+i) and type the following with the appropriate file open in your editor:

document.getElementsByTagName('atom-text-editor')