rack middleware chaining

rack_chaining.rb

class M
  def initialize(app)
    @app = app
  end
  
  def call(env)
    puts "Before call in middleware #{self.class}"
    response = @app.call(env)
    puts "After call in middleware #{self.class}"
    response
  end
end

class A < M
end

class B < M
end

class C < M
end

app = lambda do |env|
  puts "I am the endpoint app"
  [
    200,
    { "Content-Type" => "text/html" },
    ["I'm the endpoint"]
  ]
end


use A
use B
use C
run app

A.new(B.new(C.new(app))))