Dealing with Errors

import IEx.Helpers

Let it crash

# spawn_link fn -> 1 / 0 end

# spawn_link fn -> raise "booM!" end

i + 1

Errors as Data

{:error, "some message"}

:error

# Integer.parse("42 apples") # {42, " apples"}
Integer.parse("I have 42 apples")

Errors as Exceptions

# String.to_integer("42") # 42
String.to_integer("")

How to cause them

1 / 0

hd []

List.first([])

raise "Oops..."

raise RuntimeError, "bad things, man..."

raise ArgumentError, "bad things, man..."

ArgumentError.__struct__

# or
%ArgumentError{}

How to customize them

defmodule MyException do
  defexception message: "Whoa... that went poorly..."
end

raise MyException

raise MyException, "mistakes were made..."

How to eal with them

try do
  raise "booM!"
rescue
  e -> RuntimeException
    {:error, e.message}
end

try do
  cond do
    Enum.random([1, 2]) == 1 -> {:ok, 1}
    true -> raise "boom"
  end
rescue
  e -> RuntimeException
    {:error, e.message}
end

try do
  cond do
    Enum.random([1, 2]) == 1 -> {:ok, 1}
    true -> raise "boom"
  end
rescue
  e -> RuntimeException
    {:error, e.message}
after
  # clean up code here
  IO.puts "cleaning up :)"
end