Question

I would like to use http://code.google.com/p/stateless in my code to separate the functionality from its dependencies. I didn’t find any advanced examples of the usage, so this question is about stateless framework best practices.

I have following configuration (this is just example, has only one function state):

var stateMachine = new StateMachine(State.Stopped);

stateMachine.Configure(State.Stopped)
    .Permit(Trigger.Failed, State.Error)
    .Permit(Trigger.Succeed, State.GenerateMachineData);

stateMachine.Configure(State.GenerateMachineData)
    .Permit(Trigger.Failed, State.Error)
    .Permit(Trigger.Succeed, State.Finished);

public enum State
{
    Stopped,
    GenerateMachineData,
    Finished,
    Error
}

public enum Trigger
{
    Succeed,
    Failed
}

where to call the actual functionality then. I had following ideas but each of them has advantages and disadvantages:

1) Set the functionality as well as next fire in OnEntry():

stateMachine.Configure(State.GenerateMachineData)
.OnEntry(() => { 
    try {
       Generate(); 
       stateMachine.Fire(Trigger.Succeed);
    } catch {
       stateMachine.Fire(Trigger.Error);
    } 
})
.Permit(Trigger.Failed, State.Error)
.Permit(Trigger.Succeed, State.Finished);

so then if I just call

stateMachine.Fire(Trigger.Succeed);

it ends up either in State.Finished or State.Error

• advantages – all together
• disadvatages – the solution cant be really unittested

2) have statemachine and functionality separated like:

void DoTheStuff() {
    switch (stateMachine.State)
    {
         State.Stopped:
              stateMachine.Fire(State.Succeed);
              break;
         State.GenerateMachineData:
              Generate();
              stateMachine.Fire(State.Succeed);
              break;
         default:
              throw new Exception();
    }
}


void Main()
{
    while (stateMachine.State != State.Succeed && stateMachine.State != State.Error)
    {
        DoTheStuff();
    }
}

• advantages: the statemachine can be tested itself
• disadvantages: I quite don't like it

3) some other solution?

I will be glad for any answer

Answer 1

I like BugTrackerExample which they have in source code.

So your machine would probably look like this:

class Generator
{
    private readonly StateMachine state;

    public Generator()
    {
        state = new StateMachine(State.Stopped);

        // your definition of states ...

        state.Configure(State.GenerateMachineData)
        .OnEntry(() => { Generate(); })
        .Permit(Trigger.Failed, State.Error)
        .Permit(Trigger.Succeed, State.Finished);

        // ...
    }

    public void Succeed()
    {
        state.Fire(Trigger.Succeed);
    }

    public void Fail()
    {
        state.Fire(Trigger.Fail);
    }

    public void Generate()
    {
        // ...         
    }
}

In this case tests shouldn’t be problem.

If you need further separation you can use event, delegate or strategy pattern instead of Generate method.