Agile Web Development with Rails 5, 1st Edition

Objects and Operations That Span Requests

While the bulk of the state that persists across requests belongs in the database and is accessed via Active Record, some other bits of state have different life spans and need to be managed differently. In the Depot application, while the Cart itself was stored in the database, knowledge of which cart is the current cart was managed by sessions. Flash notices were used to communicate simple messages such as “Can’t delete the last user” to the next request after a redirect. And callbacks were used to extract locale data from the URLs themselves.

In this section, we will explore each of these mechanisms in turn.

Rails Sessions

A Rails session is a hash-like structure that persists across requests. ...