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Any device that changes its state from one to another due to some actions are defined to be state machines. For example an ATM machine, traffic signal, remote control, the computer itself, etc. Most software applications also depend and operate based on the state. There are two types of state machines.
成都创新互联长期为上千家客户提供的网站建设服务，团队从业经验10年，关注不同地域、不同群体，并针对不同对象提供差异化的产品和服务；打造开放共赢平台，与合作伙伴共同营造健康的互联网生态环境。为合山企业提供专业的成都做网站、网站设计，合山网站改版等技术服务。拥有十余年丰富建站经验和众多成功案例,为您定制开发。1. Finite state machine – A state machine holding a defined set of states and they work within that.
2. Infinite state machine – Here the states can be many and cannot be predefined.
Most common state machines are finite ones
The following things collectively make an effective finite state machine.
A defined set of states. At any point of time the state machine will be in any one of the defined states. For example Red, Green and Yellow in a traffic signal system.
A state machine changing its state from one to another is called State Transition. Usually there will be a state transition table built that will contain the state sequences and also metadata saying which event will cause which state transition.
Triggers are the points that induce the state transition in a state machine.
Actions are performed by the state machines when a particular state is attained and exited. There will be Entry and Exit actions for each state.
This is the piece of component that validates the transition and ensures that no invalid state changes are carried out.
State Transition Table:
The turnstile state machine can be represented by a state transition table, showing for each state the new state and the output (action) resulting from each input
| Current State | Input | Next State | Output |
|---|---|---|---|
| Locked | coin | Unlocked | Unlock turnstile so customer can push through |
| push | Locked | None | |
| Unlocked | coin | Unlocked | None |
| push | Locked | When customer has pushed through, lock turnstile |
State machine 和 软件设计模式里面的 state pattern 是有区别的。
实现 State machine 并不一定需要用 State pattern, 模式。
但是用 state pattern 模式来实现状态机比较清晰和易于理解。
关于State machine . 这里有篇很好的文章：
https://docs.microsoft.com/en-us/dotnet/framework/windows-workflow-foundation/state-machine-workflows