richmolj

# not real code
module Rack
  class Director
    def call(env)
      @request = Rack::Request.new(env)
      status, headers, body = @app.call(env)
      @response = Rack::Response.new(body, status, headers)
      if authenticated?
        # inject toolbar
      end

richmolj

class MyUploader < CarrierWave::Uploader::Base
  def store_dir
    Configuration[:store_dir]
  end
end

richmolj

class Delay
  def by
    # complex logic
    result = yield
    # complex logic
    result
  end
end

class Post

richmolj

class Post
  def publish
    self.published_at = Delay.by(Configuration[:delay_time])
    save
  end
end

richmolj

class HttpRequestWrapperGem
  def request(uri)
    config.backend.get uri
  end
end

HttpRequestWrapperGem.configure do |c|
  c.backend = SearchVersion2.new
end

richmolj

1. If something is simple and <30%* likely it will be changed, don't DI for DI's sake:

• This is probably a sliding scale depending on the scenario. 30% is obviously a loose guideline and serves as a jumping-off point. Just know it's not 90%.

Example 1 (Encrypter)
Example 2 (simple published_at)

2. When something is <30% likely to change, but getting complicated:

Add a class if this is a separate responsibility:

richmolj

# when running cron jobs

module PutsOverride
  def puts(*stmt)
    if Configuration[:redirect_puts]
      # write the stmt to custom log file for this cron
    else
      super(*stmt)
    end
  end

richmolj

around_filter :set_time_zone
 
def set_time_zone
  begin
    old_time_zone = Time.zone
    Time.zone = current_user.time_zone if logged_in?
    yield
  ensure
    Time.zone = old_time_zone
  end

richmolj

class Post
  def initialize(backend)
    @backend = backend
  end
  
  def all
    @backend.all
  end
end
Post.new(DB::Post.new)

richmolj

class Post
  def all
    Config[:backend].all
  end
end