Swap

The library that allows you to swap modules implementations in your app. Very handy for testing purposes. No need to define complex mocks, behaviours, configs…

CHANGELOG

Special thanks to llxff for great advices!

Installation

def deps do
  [{:swap, "~> 1.1.1"}]
end

Usage

Global swap

You can define a global swap of modules with a specific module (placed, for example in /lib directory):

defmodule DepsContainer do
  use Swap

  # when: can be ommited, an expression should return boolean value
  swap SomeDependency, TestImplementation, when: Mix.env() == :test
  swap SomeDependency, DevImplementation, when: Mix.env() == :dev
  swap SomeDependency, ProdImplementation, when: SomeModule.some_func()
end

In this example the first argument module will be replaced with the second argument module in certain environment. You can define multiple implementations per dependency, as well as multiple environments for a swap.

Revert swap

defmodule Dependency do
  def run, do: "dependency"
end

defmodule Implementation do
  def run, do: "implementation"
end

defmodule Test do
  use Swap

  def call do
    swap Dependency, Implementation

    Dependency.run()
  end

  def call2 do
    revert Dependency

    Dependency.run()
  end
end

Here call/0 function returns "implementation" and call2/0 returns "dependency" again.

Swap for a peace of code

You can swap modules for some peace of code. Just wrap that code into swap do block:

defmodule Dependency do
  def run, do: "dependency"
end

defmodule Implementation do
  def run, do: "implementation"
end

defmodule Test do
  use Swap

  def call do
    swap Dependency, Implementation do
      Dependency.run()
    end
  end

  def call2, do: Dependency.run()
end

Here call/0 function returns "implementation" and call2/0 returns "dependency".

For more cases see /test directory ;)

Please note

There is no circular dependency check at the moment. Be careful.

LICENSE

Copyright © 2018 Andrey Chernykh ( andrei.chernykh@gmail.com )

This work is free. You can redistribute it and/or modify it under the
terms of the MIT License. See the LICENSE file for more details.