Tiny little fluent state machine for .NET
Inspired by Martin Fowler's DSL Book, Ruby's ActsAsStateMachine gem, and Workflow Foundation's bloat.
- Simple, embeddable
- Does not ask application to conform to its framework. Just drops into any class to give it simple state machine abilities.
- Fast and efficient - Designed to be instantiated statically. A given StateMachine is itself stateless, and transforms the state of StateModels passed to it.
- Keeps the state where it belongs, on the model itself. Not serialized elsewhere.
- Provides all the plumbing necessary: states, transitions, triggers, callbacks, machines
- Fluent API
- Describe your state machine, it's transitions, triggers, callbacks, etc. in a minimal, readable, english-like C# syntax, all without repeating yourself.
- Fluent API is implemented with a Nate state machine, itself.
- Flexible
- Support for multiple identical triggers per state with varying targets, chosen from at runtime via lambda expression guards
- Support for globally-available transitions which provide a pragmatic way to always allow short-circuits
- Exposure of Underlying State Machine model allows for more advanced possibilities
An example implementing Martin Fowler's Gothic Security DSL Sample, demonstrating a portion of the Fluent API.
http://martinfowler.com/dslwip/Intro.html#TheStateMachineFramework
The state machine is described succinctly and embedded directly within the StateModel, which holds (and probably persists) the current state.
public class MissGrantController : IStateModel
{
/* state is stored on the model */
public object CurrentState { get; set; }
public MissGrantController() { CurrentState = securityControllerStateMachine.InitialState; }
/* state machine is described once, statically */
private static IFluentStateMachine<MissGrantController>
securityControllerStateMachine = FluentStateMachine<MissGrantController>.Describe()
.State("idle")
.AfterEntry(e => {
e.Model.UnlockDoor();
e.Model.LockPanel(); })
.TransitionsTo("active").On("doorClosed")
.Initiates()
.State("active")
.TransitionsTo("waitingForLight").On("drawOpened")
.TransitionsTo("waitingForDraw").On("lightOn")
.State("waitingForLight")
.TransitionsTo("unlockedPanel").On("lightOn")
.State("waitingForDraw")
.TransitionsTo("unlockedPanel").On("drawOpened")
.State("unlockedPanel")
.AfterEntry(e => {
e.Model.UnlockPanel();
e.Model.LockDoor(); })
.TransitionsTo("idle").On("panelClosed")
.GloballyTransitionsTo("idle").On("doorOpened")
.Compile();
/* external controls */
public void DoorClosed() { securityControllerStateMachine.Trigger("doorClosed", this); }
public void DrawOpened() { securityControllerStateMachine.Trigger("drawOpened", this); }
public void LightOn() { securityControllerStateMachine.Trigger("lightOn", this); }
public void DoorOpened() { securityControllerStateMachine.Trigger("doorOpened", this); }
public void PanelClosed() { securityControllerStateMachine.Trigger("panelClosed", this); }
/* locking/unlocking actions */
private void UnlockPanel() { Console.WriteLine("Unlocking Panel"); }
private void LockPanel() { Console.WriteLine("Locking Panel"); }
private void LockDoor() { Console.WriteLine("Locking Door"); }
private void UnlockDoor() { Console.WriteLine("Unlocking Door"); }
}
The MIT License
Copyright (c) 2009-2011 Michael Monteleone
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.