@elementree/state-machine
v0.2.4
Published
FSM (Finite State Machine) state factory for use with Elementree
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@elementree/state-machine
FSM (Finite State Machine) state factory for use with Elementree
Example
<!DOCTYPE html>
<html>
<body>
<script type="module">
import { merge, prepare, render } from 'https://unpkg.com/elementree'
import createStateMachine from 'https://unpkg.com/@elementree/state-machine'
const State = createStateMachine({
initial: 'liquid',
liquid: {
freeze: 'solid',
boil: 'gas',
value: '60F'
},
solid: {
melt: 'liquid',
value: '32F'
},
gas: {
chill: 'liquid',
value: '212F'
}
})
function View (state) {
return render`
<body>
<p>${state.state} ${state.value}</p>
${Object.keys(state.transition).map(t => {
return render`<button onclick=${onClick(t)}>${t}</button>`
})}
</body>
`
function onClick (to) {
return () => state.transition[to]()
}
}
merge('body', prepare(View, State))
</script>
</body>
</html>API
import createStateMachine from 'https://unpkg.com/@elementree/state-machine'createStateMachine(states: Object) -> Object
To create an instance of a StateMachine pass a 'states' object. A valid 'states' object must have, at a minimum, a single state. And an initial property which is set to a valid state property.
There are two types of machine definitions: "active" and "passive". If the definition includes names for each valid transition it is an "active" definition and the transition property will include active functions (like freeze() and boil()). An example of an "active" definition is:
createStateMachine({
initial: 'liquid',
liquid: {
freeze: 'solid',
boil: 'gas',
value: '60F'
},
solid: {
melt: 'liquid',
value: '32F'
},
gas: {
chill: 'liquid',
value: '212F'
}
})A "passive" definition uses the to property on each state indicating one or more valid states the current state can transition to. For a "passive" definition, the transition property will only include "passive" functions (like toSolid and toGas). An example of an "passive" definition is:
createStateMachine({
initial: 'liquid',
liquid: {
to: ['solid', 'gas']
value: '60F'
},
solid: {
to: 'liquid'
value: '32F'
},
gas: {
to: 'liquid'
value: '212F'
}
})<StateMachine>.state -> String
Return the string name of the StateMachine state.
<StateMachine>.value -> Any
value returns the value (object or primitive) of the current state if one exists and returns undefined if not.
<StateMachine>.transition -> Object
transition is an object with a collection of functions allowing the developer to avoid
transitioning using the string names. In the example above, when in the liquid state, two passive and two active functions exist on transition. The passive functions are transition.toSolid, transition.toGas. The two active functions are transition.freeze and transition.boil. All state specific functions on transition accept a single value argument.