OK Elixir

Effecient error handling in elixir pipelines. See Handling Errors in Elixir for a more detailed explination

Installation

Available in Hex, the package can be installed as:

  1. Add ok to your list of dependencies in mix.exs:

    def deps do 

     [{:ok, "~> 0.0.1"}]

    end

  2. Refetch the dependencies, execute:

    $ mix deps.get

Usage

The OK module works with the native error handling in Erlang/Elixir, that is a result tuple. A result tuple is a two-tuple tagged either as a success(:ok) or a failure(:error).

{:ok, value} | {:error, reason}

Bind

The primary functionality is the OK.bind/1 function. This function takes a result tuple and a next function. If the result tuple is tagged as a success then it will be passed to the next function. If the tag is failure then the next function is skipped

OK.bind({:ok, 2}, fn (x) -> {:ok, 2 * x} end)
# => {:ok, 4}

OK.bind({:error, :some_reason}, fn (x) -> {:ok, 2 * x} end)
# => {:error, :some_reason}

'~>>' Macro

This macro allows pipelining results through a pipeline of anonymous functions.

import OK, only: :macros

def get_employee_data(file, name) do
  {:ok, file}
  ~>> &File.read/1
  ~>> &Poison.decode/1
  ~>> &Dict.fetch(&1, 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

Success

Wraps a value in a successful result tuple.

OK.success(:value)
# => {:ok, :value}

failure

Wraps a reason in a failure result tuple.

TODO