Building a state machine

Question

4.00/5 (1 vote)

See more:

I'm looking at creating a state machine for a project. The project will have many algorithms each having a state machine in it. Returning an enumeration for the next state would pollute a base class enumeration, so not really thrilled about that.

Below is working code that I came up with. Not crazy about the return type of object but don't really see a way around it.

Anyone have any thoughts?

What I have tried:

C#

using System;

namespace StateMachine
{
	/// 
	public class StateMachine2BaseClass
	{
		protected void RunAlgorithm(Func<object> nextState)
		{
			while (nextState != null)
			{
				var currentState = nextState;
				nextState = (Func<object>)currentState();
			}
		}

		protected Func<object> End()
		{
			return null;
		}
	}

	/// 
	public class StateMachine2 : StateMachine2BaseClass
	{
		private int count;

		public void Run()
		{
			RunAlgorithm(Start);
		}

		private Func<object> Start()
		{
			Console.WriteLine("Start");
			return Step_1;
		}

		private Func<object> Step_1()
		{
			if (++count > 5)
				return Step_2;

			Console.WriteLine("Step 1");

			return Step_1;
		}

		private Func<object> Step_2()
		{
			Console.WriteLine("Step 2");
			return End;
		}
	}
}

Posted 7-Oct-16 3:14am

Dave Elliott

Updated 7-Oct-16 4:09am

Add a Solution

Comments

F-ES Sitecore 7-Oct-16 9:35am

Rather than using functions to define your state you're better using classes. It might mean more coding but it'll be more flexible and type safe.

http://www.codeproject.com/Articles/43356/A-Simple-State-Machine

If you google "c# state machine" you'll find other examples too.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Answer 1 · 2016-10-07T04:09:00

As F-ES Sitecore suggests, a class - based approach would work better.
Define an abstract State class which declares an abstract DoWork method, taking as a parameter the "machine info" class which describes the information the states will operate on, if any and returning a State instance.

Then for each state you need, define a new class derived from the State class and implement the DoWork method for each.

All you have to do then is:

C#

protected void RunAlgorithm(Func<object> nextState)
    {
    State currentState = new FirstState();
    while (currentState != null)
        {
        currentState = currentState.DoWork(machineInfo);
        }
    }

The system will sort out which DoWork method it needs to call each time.