What is an Anti pattern?

What is an Anti pattern as compared to say design patterns in general and are they unique only to Rails?

In software engineering, an anti-pattern (or antipattern) is a pattern that may be commonly used but is ineffective and/or counterproductive in practice.

Cheers,
Greg Funston SCJP

Congrats on what looks like a fine book for users of the Ruby framework. I look forward to reading it sometime.

Cheers,
Greg Funston SCJP

Praful Gupta wrote:are they unique only to Rails?

Well design patterns are generally mostly language independant, so anti patterns probably are simular I think, right?

Yes, loosely speaking, anti-pattern is something that is routinely done in a wrong manner. For example beginners learning struts or php coders coming into Rails frequently write scriptlets because they seem more powerful/easy for their tasks.

Thus, anti-patterns are opposite of design patterns when it comes to applicability. DPs provide a guidemap for development/learning whereas anti-DPs educate us on common pitfalls in development.
As rails packs with itself a lot of stuff under the hood, like MVC, ORM & RESTful architecture, we frequently find ourselves having a poor or non-eloquent design. Here's when books like these help you out.