Elixir

Functional highly scalable language for realtime data built on Erlang VM allowing usage of Erlang libs/functions like OTP.

Ruby on Rails-like immutable, dynamically typed, functional language

Runs inside lightweight threads(called processes) communicating via messages even if on different machines so legit horizontal scale(Erlang VM handles multi-machine, can also implement with Redis)

Elixir uses supervisers and processes fail fast. If there is an error, restart in proper/known state

  • Hex package manager

  • Elixir used by Brex, Tandem, Pagerduty

  • Inline code tests

  • Pure Functional

    • no class with internal state, but modules that init or transform an input state and return new state

    • Not indexable list, but recursive head rest pattern matching

  • To dealing with state across processes, use Erlang Term Storage(ETS) or processes like Agents, Genserver

  • Opinated(variables must be camelcase and modules CamelCase)

Basic

  • Double and triple equals like javascript(type conversion vs no type conversion)

  • if age === 18 do [.] else [.] end, ruby unless, switch => case, long if else can be cond similar to Ocaml

  • Like erlang, function returns the last value

  • Can't do for (int ....) b/c immutable, must use recursion

  • = operator is actually called the match operator

  • someFunction/2 means someFunction with two args as functions unique by name & arg count(arity)

  • or, and, not and can short circuit

  • ==, !=, ===(doesn't count integers and floats as equal, but works at comparing native objects! [1,2] === [1,2]), !==, <=, >=, < and >

  • Use pin operator ^ to pattern match against variables cur value: x = 1 ^x = 2 => Error no match 1 = 2 ( apparently also used in queries for type coercion)

  • "a" is UTF-8 encoded binary while 'a' is charlist

test.exs

#comments
defmodule M do
	def main do
		do_stuff()		
	end
	
	def do_stuff do
		my_str = "My Sentence"
		IO.puts "Length: #{String.length(my_str)}"
		IO.puts not true
		1
	end
end

Doesn't actually need main or anything

IO

Print internal representation

IO.inspect String.split(longer_str, " ") 
IO.write "No newline"
a = "hi"
IO.puts "Puts with newline #{a}" 
IO.puts(:stderr, "error bb")
x = IO.gets("yes or no?") #prompts user and return string with newline

(1..10)
|> IO.inspect #returns param for easy pipe usage
|> Enum.map(fn x -> x * 2 end)

IO.inspect [97, 98] => [a,b]

IO.inspect [97, 98], char_lists: :as_lists => [97, 98]

Branches

age = 16
if age >= 18 do
	IO.puts "Can Vote"
else #no else if
	IO.puts "Can't Vote" 
end

unless age === 18 do 
	IO.puts "You're not 18"
else 
	IO.puts "You are 18"
end

Trenary op

canvote = if age > 18, do: "Can Vote", else: "Can't Vote"
if 0, do: "printed", else: "not printed" #if checks for nil or false, anything else is true

Conditional Matching, goes to first match

cond do #checks list of conditions
	x -> IO.puts "You can vote"
	age >= 16 -> IO.puts "You can drive"
	age >= 14 -> IO.puts "You can wait"
	true -> IO.puts "Default"
end

switch

case x do
	1 -> :one
	2 -> :two
	n when is_integer(n) and n > 2 -> :larger_than_two
end
  
case Chat.get_chat_message(message_id) do
  %ChatMessage{} = chat_message ->				  
  	Chat.delete_chat_message(chat_message)

  nil -> nil
end

With

with {:ok, user} <- create_user(user_params),
     {:ok, email} <- Mailer.compose_email(user) do
  {:ok, Mailer.send_email}
else
  {:error, _reason} ->
    handle_error
end

with user_id when not is_nil(user_id) <- get_session(conn, :user_id),
       user when not is_nil(user) <- Repo.get(User, user_id)
  do
    assign(conn, :current_user, user)
  else
    _ ->
      conn
      |> Controller.put_flash(:error, "You have to sign in to access this page.")
      |> Controller.redirect(to: "/sign_in_links/new")
      |> halt
  end

In the code snippet above we've rewrite nested case clauses with with. Within with we invoke some functions (either anonymous or named) and pattern match on their outputs. If all matched, with return do block result, or else block result otherwise.

We can omit else so with will return either do block result or the first fail result.

System Variables

 System.get_env("POSTMARK_API_KEY")

Type Converstion

Integer.to_string(123) #"123"
String.to_integer("123") #123
String.to_integer("abc") #(Argument Error)
Integer.parse("123") #{123, ""}
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