How unidirectional data flow in pure Unity might work (inspired by Redux, Vuex, etc.), minus UniRx. Assumes Zenject for dependency injection. Latest: https://github.com/lux/reactive-tests

TutorialActions.cs

// Business logic
public class TutorialActions {
	private State _state;

	[Inject]
	private void Init (TutorialState state) {
		_state = state;
		
		// Fetch latest from database then call _state.SetSteps()
		// and _state.SetCurrentStep()
	}
	
	public void NextStep () {
		// Business logic, sync to web, etc. then update local state

		_state.IncrementStep ();
	}
}

TutorialState.cs

// State mutations
public class TutorialState {
	public delegate void StepChanged (int step);
	public StepChanged OnStepChanged;
	
	public delegate void Complete ();
	public Complete OnTutorialComplete;

	public delegate void StepsReady (Step[] steps);
	public StepsReady OnStepsReady;
	
	public delegate void ErrorOccurred (string err);
	public ErrorOccurred OnError;

	public class Step {
		public string title;
		public string instructions;
	}
	
	private Step[] steps;
	private int step = 0;
	
	// Called by action during initializations
	public void SetSteps (Step[] steps) {
		this.steps = steps;
		
		if (OnStepsReady != null) OnStepsReady (steps);
	}
	
	// Called by action during initializations
	public void SetCurrentStep (int cur) {
		// Validations
		if (cur < 0) {
			if (OnError != null) OnError ("Can't set step below zero");
			return;
		}
		
		if (cur >= steps.Length) {
			if (OnError != null) OnError ("Can't set step above number of steps in tutorial");
			return;
		}
		
		step = cur;
		
		if (OnStepChanged != null) OnStepChanged (step);
	}
	
	public void IncrementStep () {
		if (step + 1 == steps.Length) {
			if (OnTutorialComplete != null) OnTutorialComplete ();
			return;
		}
		
		step++;
		
		if (OnStepChanged != null) OnStepChanged (step);
	}
}

TutorialStepView.cs

public class TutorialStepView : MonoBehaviour {
	private TutorialActions _actions;
	private TutorialState _state;

	private int currentStep;

	[Inject]
	private void Init (TutorialActions actions, TutorialState state) {
		_actions = actions;
		_state = state;
	}
	
	private void OnEnable {
		_state.OnStepChanged += HandleStepChanged;
		_state.OnTutorialComplete += HandleCompleted;
		_state.OnError += HandleError;
	}
	
	private void OnDisable () {
		_state.OnStepChanged -= HandleStepChanged;
		_state.OnTutorialComplete -= HandleCompleted;
		_state.OnError -= HandleError;
	}

	// Handle next step button clicks
	public void NextStep () {
		_actions.nextStep ();
	}

	public void HandleStepChanged (int step) {
		// Update UI with next step
		
		currentStep = step;
	}
	
	public void HandleCompleted () {
		// Update UI to show tutorial completed
	}
	
	public void HandleError (string err) {
		// Handle errors
		Debug.LogError (err);
	}
}