[Qt-interest] Resolving nearly orthogonal paralle states

[Neil Eccles]

Can anyone help  a state machine user newbie.

 

I have an app that needs to enable a widget depending on the current state
of two orthogonal states:- 

 

i.e. I  have two parallel  states each with a true false states in side them

 

Qstate *top = new QState(::ParallelStates);

Qstate *a = new QState(top);

QState *b = newQState(top);

 

Qstate *aTrue = new QState(a);

Qstate *aFalse = new QState(a);

 

Qstate *bTrue = new QState(b);

Qstate *bFalse = new QState(b);

 

Also the intial states are

 

a->intialState(aFalse);

b->initialState(bFalse);

 

The truth table for the widget to be enabled is

 

              B:True      B:False

A:True enabled  false 

A:False false       false

 

I am trying to work out how to use the state machine to look after setting
the enable/disabled for this widget.

 

Ideas I have had so far include:-

1.Having one state engine with  the combinations of a and b as unique states
ie aTrue and bTrue; aFalse and bTrue but this seems bad coding from a
scaling up principle

2 Creating two properties inside the widget and setting these when the
states transition and letting the widget decide if it is enabled or disabled
(this seems to be moving the state engine mechanics into the widget and
hiding it, however it could be argued that it is encapsulating it exactly
where it is needed).

3. put a third parallel state with widgetEnabled and WidgetDisabled and
trying to use guarded transitions. However, I believe that the transition
guard will be dependent on the other parallel state for example going from
state aFalse to aTrue should only cause a transition to widgetEnabled if
bTrue is also set.

 

Or am I just missing the point and going around in circles?

 

Finally,  I suspect that I am not looking at the state diagram from the
right angle and will become very clear if the diagram is massaged.

 

Thanks

 

Neil Eccles 

 

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Dr. Neil C. Eccles

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