4.7. Filters

Filters enable controllers to run shared pre and post processing code for its actions. These filters can be used to do authentication, caching, or auditing before the intended action is performed. Filter declarations are macro style class methods, that is, they appear at the top of your controller method, inside the class context, before method definitions. We also leave off the parentheses around the method arguments, to emphasize their declarative nature, like this:

before_filter :require_authentication