Simple way to load Rails plugins in Sinatra

plugin_loader.rb

# Simple bootloader for Rails plugins in Sinatra
# This checkes the +plugin_folder+ for plugin-like bundles. For each folder it finds it will do:
#   If the +lib+ folder exists: add it to our load path
#   If a +init.rb+ file exists: require it
# Not very robust but it is lightweight for loading simple rails plugins
class PluginLoader
  attr_reader :plugin_folder
  
  def initialize(plugin_folder)
    @plugin_folder = plugin_folder
    self
  end
  
  def load_plugins!
    Dir[File.join(plugin_folder, '*')].sort.each do |plugin|
      if File.directory?(plugin)
        init_file = File.join(plugin, 'init.rb')
        lib_folder = File.join(plugin, 'lib')
        
        if File.directory?(lib_folder)
          $: << lib_folder
        end
    
        if File.exist?(init_file)
          require init_file
        end
      end
    end

    $:.uniq!
  end
end

usage.rb

require 'plugin_loader'

# This is the path to wherever your plugins folder is located
plugin_root = File.expand_path('../../plugins', __FILE__)
PluginLoader.new(plugin_root).load_plugins!