dart_state_machine

Description:

dart state machine

A general purpose finite-state machine for Dart developers.
This package is a port of the Kotlin version of the state machine.
Usage #
Let's suppose your app wants to use a state machine for user session state management.
First, let's create your MySessionEvent and MySessionState classes (an implementation of the
library's StateMachineEvent and StateMachineState abstract classes):
import 'package:dart_state_machine/dart_state_machine.dart';

class MySessionEvent implements StateMachineEvent {
static const MySessionEvent login = MySessionEvent._('login');
static const MySessionEvent logout = MySessionEvent._('logout');
static const MySessionEvent logoutAndForget = MySessionEvent._('logout_and_forget');

final String id;

const MySessionEvent._(this.id);

@override
bool operator ==(Object other) =>
identical(this, other) ||
other is MySessionEvent && runtimeType == other.runtimeType && id == other.id;

@override
int get hashCode => id.hashCode;

@override
String toString() => '$id';
}

class MySessionState implements StateMachineState {
static const MySessionState active = MySessionState._('active');
static const MySessionState inactive = MySessionState._('inactive');
static const MySessionState forgotten = MySessionState._('forgotten');

final String id;

const MySessionState._(this.id);

@override
bool operator ==(Object other) =>
identical(this, other) ||
other is MySessionState && runtimeType == other.runtimeType && id == other.id;

@override
int get hashCode => id.hashCode;

@override
String toString() => '$id';
}
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Then it is possible to create a StateMachine using a StateMacnineBuilder:
var stateMachine = StateMachineBuilder<MySessionEvent, MySessionState>()
.setInitialState(MySessionState.active)
.addTransition(
Transition(
event: MySessionEvent.login,
statePath: [MySessionState.inactive, MySessionState.active]
)
)
.addTransition(
Transition(
event: MySessionEvent.logout,
statePath: [MySessionState.active, MySessionState.inactive]
)
)
.addTransition(
Transition(
event: MySessionEvent.logoutAndForget,
statePath: [MySessionState.active, MySessionState.forgotten]
)
)
.build();
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Meaning of the above sample configuration is that:

There are 3 possible session states (active, inactive and forgotten).
There are 3 possible events (login, logout and logoutAndForget).
StateMachine's initial state is ACTIVE.
There are 3 possible state machine transitions:




Event
State path




login
inactive -> active


logout
active -> inactive


logoutAndForget
active -> forgotten



Now, we can attach a listener and play with the state machine a bit:
var listener = (MySessionState oldState, MySessionState newState) =>
print('state change: $oldState -> $newState');

stateMachine.addListener(listener);

// prints "state change: active -> inactive"
var consumed = stateMachine.consumeEvent(MySessionEvent.logout);
assert(consumed);

// does nothing
consumed = stateMachine.consumeEvent(MySessionEvent.logout);
assert(!consumed);

// prints "state change: inactive -> active"
consumed = stateMachine.consumeEvent(MySessionEvent.login);
assert(consumed);

// does nothing
consumed = stateMachine.consumeEvent(MySessionEvent.login);
assert(!consumed);

// prints "state change: active -> forgotten"
consumed = stateMachine.consumeEvent(MySessionEvent.logoutAndForget);
assert(consumed);

// does nothing
consumed = stateMachine.consumeEvent(MySessionEvent.login);
assert(!consumed);

// does nothing
consumed = stateMachine.consumeEvent(MySessionEvent.logout);
assert(!consumed);
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License #

MIT License
Copyright (c) 2021 Vitaliy Khudenko
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.