Sinatra commands do not work in modules - ruby

Question

I have a Sinatra app which requires a module in a different file. When I use Sinatra commands in that module (e.g. redirect "http://facebook.com"), I get a NoMethodError. To illustrate the problem, I have made a simplified version:
--- mainapp.rb ---
#config
require './redirector.rb'
get '/' do
Redirector::redirect_to_stackoverflow
end
--- redirector.rb ---
module Redirector
require 'sinatra'
def self.redirect_to_stackoverflow
redirect "http://stackoverflow.com"
end
end
--- config.ru ---
require 'rubygems'
require 'sinatra'
require File.dirname(__FILE__) + "/ptt.rb"
run Sinatra::Application
What is wrong? Is there a place where I haven't required something properly?

Answer 1

The call to redirect inside the Redirector module is sent to the Redirector Module object, where the method does not exist. require 'sinatra' inside module Redirector is not necessary, and does not do any kind of method composition.
You probably could compose Sinatra methods into your Redirector module, but that is not normal practice. Usually it's the other way around - you write "helper" modules that are composed in to your Sinatra application in various ways.
This is a similar example application, with a more usual approach to composition:
app.rb
require 'sinatra'
require_relative 'redirect.rb'
class MyApp < Sinatra::Application
include Redirector
get '/' do
redirect_to_stackoverflow
end
end
redirect.rb
module Redirector
def redirect_to_stackoverflow
redirect "http://stackoverflow.com"
end
end
config.ru
require File.dirname(__FILE__) + "/app.rb"
run MyApp

Answer 2

#Neil Slater's explanation is correct, but I'd suggest you also make it an Sinatra extension, e.g.
require 'sinatra/base'
module Sinatra
module Redirector
def redirect_to_stackoverflow
redirect "http://stackoverflow.com"
end
end
helpers Redirector
end
Then (for a classic app) all you need to do is require it.
require 'sinatra/redirector'
get "/" do
redirect_to_stackoverflow
end