NameError: uninitialized constant Dispatch

In the "Rails Way" book, following an example, I came to a point where I
had to run:

Dispatch.dispatch

But, I get the following:

irb(main):003:0> Dispatch.dispatch
NameError: uninitialized constant Dispatch
        from (irb):3

I want to mention that I'm using "Rails 3.0.0", and the book seems to
use an older version of Rails, is that the issue?

What is the command that I should run in this case?

Thanks.

It is:

Dispatcher.dispatch

But, although that, I'm getting:

irb(main):003:0> Dispatcher.dispatch
NameError: uninitialized constant Dispatcher
        from (irb):3