fsm
Finite State Machine library Uses node-graph to work with state graph.
Meanwhile, you can look at test/test.js
to see usage example.
Installation
npm install node-fsm
Usage
new FSM(machineSpec, routerFunc)
machineSpec
should contain state graph (nodes
and edges
like in node-graph
). Additional properties are currentState
that contains name of current machine state. data
contains your arbitrary data tied with fsm.
routerFunc(edge, requestData, callback)
is async function that checks, whether we made our transition successfully, or not. First argument is an edge
object represents state graph edge we attempt to follow (hint: here you can process any arbitrary data you put on edge object in state graph). At the routerFunc
completion you should call callback
, passing err
object, if you encountered any errors, and boolean variable that indicates whether we made transition or not.
routerFunc
is bound to fsm instance, so you can use this
variable to access machine object.
var machineSpec = {
nodes: [
{
name: 'A'
},
{
name: 'B',
youCanPutArbitraryDataOnYourNodes: { ... }
}
],
edges: [
{
name: 'A->B',
from: 'A',
to: 'B',
youCanPutArbitraryDataOnYourEdgesToo: { ... }
}
],
currentState: 'A',
data: { … }
}
var routerFunc = function (edge, requestData, callback) {
// Make any external calls to determine,
// whether our transition is succesfull or not
// …
callback(null, true);
}
var fsm = new FSM(machineSpec, routerFunc);
availableEdges()
Returns array of edges, that can be followed from current machine state.
var edges = fsm.availableEdges();
// Returns:
[
{
name: 'A->B',
from: 'A',
to: 'B',
youCanPutArbitraryDataOnYourEdgesToo: { ... }
}
]
follow(edgeName, [requestData], callback)
Attempt to change machine state following edge specified by edgeName
and optional requestData
that would be passed to routerFunc
(useful, since it can provide addtional info on change state attempt without modifying any of fsm data). If you omit requestData
argument, your routerFunc
will receive null
value as a second argument.
Callback should take two arguments (err, status)
, where err
will contain any errors encountered during attempt to change state, and status
will contain boolean value indication whether attempt was successful, or not.
getGraph()
Returns instance of node-graph
Graph object that you could use to navigate across fsm state graph. See docs for node-graph for methods reference.
Events
emit('state', edge)
When we successfully made a transition to a new state, fsm instance emits 'state' event, passing edge we followed as argument.
While edge object contains both from
and to
fields, you can figure out, what was previous state.
emit('terminal', edge)
When we successfully made a transition to a new state, and this state is terminal (there is no edges outbound for current state) fsm instance emits 'terminal' event, passing edge we followed as argument.
Changelog
2.0.0
Now .follow()
takes requestData
as a second argument, containing data that will be passed to routerFunc
without altering fsm. This change is backward incompatible — you should update your routerFunc
to take three arguments (see docs on routerFunc
earlier).