Generalized middleware implementation for Ruby.
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mitchellh Merge pull request #11 from invisiblefunnel/fix-undefined-local-var
Fix reference to undefined local variable
Latest commit 23d4741 Jul 3, 2014


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This is a generalized library for using middleware patterns within your Ruby projects.

To get started, the best place to look is the user guide.


This project is distributed as a RubyGem:

$ gem install middleware


Once you create a basic middleware, you can use the builder to have a nice DSL to build middleware stacks. Calling the middleware is simple, as well.

# Basic middleware that just prints the inbound and
# outbound steps.
class Trace
  def initialize(app, value)
    @app   = app
    @value = value

  def call(env)
    puts "--> #{@value}"
    puts "<-- #{@value}"

# Build the actual middleware stack which runs a sequence
# of slightly different versions of our middleware.
stack = do
  use Trace, "A"
  use Trace, "B"
  use Trace, "C"

# Run it!

And the output:

--> A
--> B
--> C
<-- C
<-- B
<-- A


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request