captain_hook

A ruby gem to decorate your methods and run arbitrary hooks before, after or around them. It is similar on how Rails does with before_action, after_action and around_action but this for any class.

It automatically wraps the configured methods to call the hooks before, after or around them.

Installation

Add the following line to your Gemfile:

gem 'captain_hook', git: 'https://github.com/factorialco/captain_hook.git', branch: 'main'

Then bundle install

Using it

In order to inject the hook behavior, you need to include the CaptainHook module in your class and use the hook method to decorate the methods you want to hook.

Registering the hooks

class MyService
  include CaptainHook

  hook :before, methods: [:cook], hook: CookHook.new, inject: [:policy_context]
  hook :before, methods: [:deliver], hook: ErroringHook.new
  hook :before,
       hook: BeforeAllHook.new,
       exclude: [:serve],
       skip_when: ->(_args, kwargs) { !kwargs[:dto] }

  hook :after, methods: [:prepare], hook: PrepareHook.new
  hook :after, methods: [:invented_one], hook: PrepareHook.new

  hook :around,
       methods: %i[serve foo],
       hook: ServeHook.new,
       skip_when: ->(_args, kwargs) { kwargs[:dto] }

  def prepare(dto:); end

  def cook; end

  def serve; end

  def deliver; end
end

Parameters:

• methods: an array of method names to hook. If not specified, it will hook all methods.
• hook: the instance of the hook to run.
• inject: The hook will receive these additional keyword arguments from the class hosting the method.
• exclude: an array of method names to exclude from being hooked.
• skip_when: a lambda that receives the positional and keyword arguments of the method being decorated and returns a boolean to skip the hook.

Implementing your hooks

You need to implement a class with the #call method. This method will receive the following positional parameters:

• klass: the class where the method is defined
• method: the method name
• block: the original method (useful for around hooks)

Additionally it will receive the positional and keyword arguments of the original method being decorated.

You can inject additional keyword parameters by using the inject parameter when registering the hook.

Caveats

• You can not call super from a child class decorated method, you will enter in an infinite loop