OK Elixir
Efficient error handling in elixir pipelines. See Handling Errors in Elixir for a more detailed explanation
Documentation for OK is available on hexdoc
Installation
Available in Hex, the package can be installed as:
Add ok to your list of dependencies in
mix.exs
:def deps do [{:ok, "~> 0.2.0"}] end
Usage
The erlang convention for functions that can fail is to return a result tuple
A result tuple is a two-tuple tagged either as a success(:ok
) or a failure(:error
).
The OK module works with result tuples by treating them as a result monad.
{:ok, value} | {:error, reason}
‘~>>’ Macro
This macro allows pipelining result tuples through a pipeline of functions.
The ~>>
macro is the is equivalent to bind/flat_map in other languages.
import OK, only: :macros
def get_employee_data(file, name) do
{:ok, file}
~>> File.read
~>> Poison.decode
~>> Dict.fetch(name)
end
def handle_user_data({:ok, data}), do: IO.puts("Contact at #{data["email"]}")
def handle_user_data({:error, :enoent}), do: IO.puts("File not found")
def handle_user_data({:error, {:invalid, _}}), do: IO.puts("Invalid JSON")
def handle_user_data({:error, :key_not_found}), do: IO.puts("Could not find employee")
get_employee_data("my_company/employees.json")
|> handle_user_data