Layered Design for Ruby on Rails Applications - Second Edition

7

State Transitions and Workflows

In this chapter, we’ll look at Rails models from a different angle, not from the persistence perspective but from the application state modeling point of view. More precisely, we will discuss the problem of describing state transitions and maintaining control over them. First, we will explore how state machines naturally emerge in Rails applications and how the same name abstraction can be used to keep the code base maintainable. Then, we will discuss the concept of a workflow, a specialized kind of state machine that represents a business process. Finally, we will consider some trade-offs of overusing state machines in code.

We will cover the following topics:

• Implicit states and transitions
• Finite-state machines ...