Hack #59. Find Out Whether Ajax Is Calling in the Request

Discover whether XMLHttpRequest or a URL in a browser is requesting an action.

One of the issues with defining simple actions in Ruby on Rails is that once an action that responds with a fine-grained value (such as a string or small HTML chunk) is defined, users can make direct requests for that little value in their browsers. But chances are, those values were designed only for XMLHttpRequest objects.

For example, “Periodically Make a Remote Call” [Hack #61] uses the request object to periodically get a string representing the current date. It calls an action named increment, which looks like this in the controller object: