Garcon

Garcon is a simple Service Locator object.

Why?

Dependencies, that's why.

Each object in your application has dependencies and related objects.

For a good design, you need to know those dependencies and keep track of them.

For a flexible design it's useful to be able to switch those dependencies in and out.

So instead of hard-coding your dependencies or injecting them as a long trail of constructor parameters, use a service locator; register your services in the locator and tell it to fetch one for you when you need it.

Your dependency map becomes a list of services - :file_server, :email_server etc.

Your implementation can be switched out at a moment's notice without affecting anything else.

You can go home relaxed and have a nice cup of tea.

Installation

Add this line to your application's Gemfile:

gem 'garcon'

And then execute:

$ bundle

Or install it yourself as:

$ gem install garcon

Usage

Create an instance of your service locator, and then register your services with it:

services = Garcon::ServiceLocator.new

services.register(:file_server) { MyFileServer.new(services) }
services.register(:path_finder) { MyPathFinder.new(services) }

Then use this Service Locator to find your related objects, instead of having hard-coded constants. For example, MyFileServer never needs to know how the Path Finder is implemented; it just needs to respond to #default.

class MyFileServer < Struct.new(:services)
  def store file
    write file: file, path: services[:path_finder].default
  end
end

file_storage = FileStorage.new(services)
file_storage.store_file my_file

If you're writing a Rails app I like to configure it like so - create your services object in config/initializers/services.rb. Then store it in your application's configuration:

services = Garcon::ServiceLocator.new
services.register(:thing_server) { ThingServer.new(services) }
MyStuff::Application.config.services = services

Then, in your application controller, add a protected method to access it:

class ApplicationController < ActionController::Base

  protected

  def services
    MyStuff::Application.config.services
  end
end

And finally you can then use it in your controllers as you wish (and then pass it on to everything else):

class MyThingsController < ApplicationController
  def index
    @things = services[:thing_server].find_all
  end
end

Alternatively, the default behaviour is to try to load a class, based upon the service name you have passed to it:

services['String'].class #=> String

Contributing

1. Fork it ( https://github.com/rahoulb/garcon/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request