Using Rack Middlware to filter parameters

[RobL <contact@robl.me>]

Hi there,

I wanted to ask if anyone could point me in the direction of some code
examples where you can use Rack Middleware to filter incoming
parameters.

Of course the classic example of middleware that does not a lot is

module Rack
  class Myfilter
    def initialize(app)
      @app = app
    end

    def call(env)
       @app.call(env)
    end
  end
end

But as a very tivial example I want be able to do something like

module Rack
  class Myfilter
    def initialize(app)
      @app = app
    end

    def call(env)
       request = Rack::Request.new(env)
       request.params.delete('someparam')
       # but at this point I want/need to modify env
       @app.call(env)
    end
  end
end

I'm not sure how I'd then get the modified env back, do you have to
literally modify something like env['query_string'], also at this
point the content length would be different so I'd have to update that
also.

Most of the applications I've seen are an endpoint and an app in
itself than sitting in the middle of the incoming request, and I'm yet
to find an example of modifying the incoming params.

Any help on this would be greatly appreciated

All the best.

RobL