Errors

Elixir has three error mechanisms: errors, throws, and exits.

Instead of all these constructs, Elixir's supervisor system is better to just fail fast and restart the app in a known state

foo + 1 # (ArithmeticError) bad argument in arithmetic expression :erlang.+(:foo, 1)

raise "oops" # (RuntimeError) oops

raise ArgumentError, message: "invalid argument foo" # (ArgumentError) invalid argument foo

Errors

Errors (or exceptions) are used when exceptional things happen in the code.

In Elixir, we avoid using try/rescue because we don’t use errors for control flow. Try/catch => try/rescue, in practice rarely used b/c tuple with err often used instead

err = try do
    5/0
rescue
    ArithmeticError -> "Can't Divide by Zero"
end
IO.puts err

Custom Errors

defmodule MyError do
    defexception message: "default message"
end

iex> raise MyError
** (MyError) default message
iex> raise MyError, message: "custom message"
** (MyError) custom message

Throws

throw and catch are reserved for situations where it is not possible to retrieve a value unless by using throw and catch.

Also uncommon

Exits

When a process dies of "natural causes" (unhandled exceptions), it sends an exit signal