promise-state-machine-es6
v2.1.0
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An event-driven finite state machine backed by Promises
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Promise State Machine ES6
This is a rewritten version of promise-state-machine but with no dependencies; not bluebird - just native ES6, DOT data generation support for use with Graphvis or vis.js, to generate a visual representation of your state machine.
Installation
npm install promise-state-machine-es6 --save
Class PromiseStateMachine
Constructor(options)
state
- May be any primitive type.
options.initial
- Initial state
.options.events
- An Object where key denotes a transition.options.events[transition].from
- From state
, may be an array of state
.options.events[transition].to
- To state
Each key defined in options.events
is defined as a method on the current instance. Use these methods to request a state transition. These methods returns a Promise that Resolves when transition succeded and Rejects when failed. To intercept a transition listen on the transition name, eg if options.events
has "warn" transition we can intercept it by fsm.on('warn', (from, to, ...rest) => Promise.resolve())
. This event would get called when fsm.warn(...rest).then()
is called.
is(...states) : Bool
Check if instance is in any state. Argument may be one or many states or an array of states.
can(...events) : Bool
Check if instance can transition to a specific state. Argument may be one or many events or an array of events.
state [getter] : state
Get current state
toDOTsync(options) : String
Synchronously create DOT file data as a string.options.replacer
- Optional synchronous replacer function that takes a data
object and returns a data
object with all values stringified.
data.from
- From state
data.to
- To state
data.transition
- Transition key
# Events
[eventsKey]
(from, to, ...arguments)
A transition event for each key of options.events
passed to the constructor may be emitted when calling any method as defined by options.events
.
transition (transitionKey, from, to, ...arguments)
This event is emitted before [transitionKey] event is emitted, returning a Promise that rejects will abort the transition and [eventsKey] event will not be emitted.
Examples
Complete Example
const fsm = new PromiseStateMachine({
initial: 'green',
events: {
warn: { from: 'green', to: 'yellow' },
panic: { from: ['green', 'yellow'], to: 'red' },
calm: { from: 'red', to: 'yellow' },
clear: { from: ['yellow', 'red'], to: 'green' }
}
});
fsm.on('warn', (from, to) => {
return Promise.resolve('result 1');
});
fsm.on('warn', (from, to, transaction, somethingElse) => {
return Promise.resolve('result 2');
});
fsm.on('transaction', (transition, from, to, ...rest) => {
transition; // => 'warn'
});
fsm.warn(transaction, somethingElse).then(function(results) {
// results: ['result 1', 'result 2']
}, function(error) {
// could receive a StateTransitionError if trying to transition via an
// inaccessible event.
});
fsm.is('green'); // => false
fsm.is('yellow'); // => true
fsm.state; // => 'yellow'
fsm.can('calm'); // => false
fsm.can('panic'); // => true
toDOTsync
const dotDataString = new PromiseStateMachine({
events: {
approve: { from: 'pending', to: 'approved' },
reject: { from: ['pending', 'approved'], to: 'rejected' },
pend: { from: ['approved', 'rejected'], to: 'pending' },
}
}).toDOTsync();
toDOTsync
const dotDataString = new PromiseStateMachine({
events: {
doWork: { from: ['Working', 'Starting'], to: 'Working' },
handleError: { from: ['Working', 'Starting'], to: 'Error' },
end: { from: ['Working', 'Starting'], to: 'End' }
}
}).toDOTsync();
Inheritance
class MyClass extends PromiseStateMachine {
constructor(options) {
super(options);
}
}
const fsm = new MyClass({
initial: 'green',
events: {
warn: { from: 'green', to: 'yellow' },
panic: { from: 'yellow', to: 'red' },
calm: { from: 'red', to: 'yellow' },
clear: { from: 'yellow', to: 'green' }
}
});
fsm.is('green'); // => true
fsm.warn().then(() => {
fsm.is('green'); // => false
});
TODO
- [ ] streamed version of toDOTsync
License
MIT