[SCXML-47] Provide a state machine support class to allow for delegation.

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Won't Do
• Affects Version/s: 0.6
• Assignee: Unassigned
• Reporter: Michael Heuer
• Created: 16/Jun/07 05:22
• Updated: 17/Oct/18 23:45
• Resolved: 17/Oct/18 23:45

Description

This is not completely thought out yet, but if folks like the idea I might persue it further.

I would like to use AbstractStateMachine but cannot extend from it:

class B extends A /*, AbstractStateMachine */ {
// copy source from AbstractStateMachine here
}

I propose here a StateMachineSupport class that provides for use by subclassing and for use by delegation. The constructors are a little messy, but in the end I have

public class StateMachineSupport {
// use by subclassing
protected StateMachineSupport(...) {
}

// use by delegation
public StateMachineSupport(Object delegator, ...) {
}

// ... methods from AbstractStateMachine
}

public abstract class AbstractStateMachine extends StateMachineSupport {
protected AbstractStateMachine(...)

{ super(...); }

}

// use by subclassing
class ConcreteStateMachine extends AbstractStateMachine {
ConcreteStateMachine()

{ super(..."stopwatch.xml"); }

public void reset()

{ ... }
public void running() { ... }

public void paused()

{ ... }
public void stopped() { ... }

}

// use by delegation
class DelegatingStateMachine extends SomethingElse {
StateMachineSupport delegate;

DelegatingStateMachine()

{ delegate = new StateMachineSupport(this, ..."stopwatch.xml"); }

public void reset()

{ ... }
public void running() { ... }

public void paused()

{ ... }
public void stopped() { ... }

}

StateMachineSupport.java, AbstractStateMachine2.java, StateMachineSupportTest.java, and AbstractStateMachine2Test.java attached.