The heart of a state machine is the transition table, which takes a state and a symbol (what you’re calling an event) to a new state. That’s just a two-index array of states. For sanity and type safety, declare the states and symbols as enumerations. I always add a “length” member in some way (language-specific) … Read more
@Ivan: There are a number of resources available on the web for Hierarchical State Machines (HSM). Miro Samek has written extensively about this design pattern and offers a lot of helpful information. Some articles that should be of interest: State-Oriented Programming (SOP) (Samek) (pdf) Hierarchical State Machines – a Fundamentally Important Way of Design (Samek) … Read more
The way I describe this difference to my colleagues is that state patterns are a more decentralized implementation of many stand alone encapsulated states whereas state machines are more monolithic. The monolithic nature of state machines means that a single state will be harder to reuse in a different machine and that it is harder … Read more
Honestly, the two patterns are pretty similar in practice, and the defining difference between them tends to vary depending on who you ask. Some popular choices are: States store a reference to the context object that contains them. Strategies do not. States are allowed to replace themselves (IE: to change the state of the context … Read more