Ajax on Rails

Chapter 2. Getting Our Feet Wet

Ho, Ajax! Once again I summon thee.

Sophocles

In this chapter, the idea is to take a walking tour, in baby steps, through some really simple Ajax examples. Rails provides a huge amount of power for doing complex Ajax interactions with very minimal code. But in order to understand what’s happening under the hood, you should be familiar with Ajax’s lowest levels (e.g., the XMLHttpRequest object). By the end, you’ll be comfortable creating XMLHttpRequest objects both by hand and by using the Prototype library. Finally, we’ll use Rails’ JavaScript helpers to create simple Ajax interactions without writing any JavaScript. With the foundation in place, you’ll have an accurate understanding of how the Rails helpers work—and also an appreciation for how much trouble they will save you.

If you’re already comfortable with Rails and basic Ajax, this chapter will be review, but you might still find it useful to at least skim the examples.

The Old-Fashioned Way

To start off, let’s do Ajax with the simplest thing that could possibly work: click a link and present a response from the server—using XMLHttpRequest directly, without Prototype or Rails’ JavaScript helpers.

Using XMLHttpRequest is often portrayed as being rocket science. But you’ll find that, with a little practice and perhaps a couple new concepts, it’s not as tricky as its reputation suggests.

Starting a Project

If you didn’t create the example Rails skeleton in the last section, do so now, from your system’s ...