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540 CHAPTER 18 Rack-based applications
will be passed as arguments to the initialize
method for this middleware, and
so this hash you’ve passed here will be the
letters argument in your middleware.
This means your LinkJumbler middleware
will replace the letter e with a anytime it
finds it in an a tag.
To see this middleware in action, let’s
fire up a server by running rails s in a ter-
Figure 18.6 What’s a Tickataa?!
minal. When you go to http://localhost:3000 you should notice something’s changed,
as shown in figure 18.6.
As you can see in this figure, your links have had their e’s replaced with a’s and any
other occurrence, such as the user’s email address, has been left untouched.
This is one example of how you can use middleware to affect the outcome of a
request within Rails; you could have modified anything or even sent a response back
from the middleware itself. The opportunities are endless. This time though, you’ve
made a piece of middleware that finds all the a tags and jumbles up the letters based
on what you tell it to.
18.5 Summary
You’ve now seen a lot of what Rack, one of the core components of the Rails stack, can
offer you. In the beginning of this chapter you built a small Rack application that
responded with OK. You then fleshed this application out to respond differently based
on the provided request. Then you built another Rack application that called this first
Rack application, running both of these within the same instance by using the
Rack::Builder class.
Next you saw how you could use these applications within the Rails stack by first
mounting your initial Rack application and then branching out into something a little
more complex, with a Sinatra-based application serving what could possibly be the
beginnings of version 3 of Ticketee’s API. Sinatra is a lightweight framework offering
the same basic features as Rails.
Finally, you saw two pieces of middleware, the ActionDispatch::Static piece and
the ActionDispatch::BestStandardsSupport. You dissected the first of these, figuring
out how it worked so that you could use that knowledge to build your own middleware,
a neat little piece that jumbles up the text on the link based on the options
passed to it.