Problem of inheritance in agents

[gbasso]

This is the same problem as events and capacities, but I din't see it for agents.

With:

agent MyAgent1
{}

agent MyAgent2 extends MyAgent1 // no error
{}

The following Java code is generated:

public class MyAgent2 extends Agent {

[gallandarakhneorg]

The generation of the correct extend type is easy to apply (done in gallandarakhneorg/sarl).
But, there is additional points to focus on if we introduce the extension mechanism for agents:

• How to call the super's implementation for a def.
• How to call the super's implementation for an event.

For illustrating, let take the following example:

agent AbstractAgent {

    uses Lifecycle

    on Initialize {
        System.out.println("Hello World in the super agent!")
    }

    def sayGoodBye {
        System.out.println("Goodbye World!")
    }

}

agent HelloChildAgent extends AbstractAgent{

    uses Schedules

    on Initialize {
        System.out.println("Hello World in the child agent!")
        in(2000)[killMe]
    } 

    def sayGoodBye {
        super.sayGoodBye()
    }

    on Destroy {
        sayGoodBye
    }
}

[gallandarakhneorg]

The FAQ or the tutorials should explain that calling an override function is possible, but not an event handler.

[gallandarakhneorg]

There is a problem to access to the inherited attributes.

[ngaud]

The idea here is to change the visibility of getter/setter methods to "protected" to enable an access to parent field from a sub-class.

[gallandarakhneorg]

Consider the SARL code:

agent A {
   var thevar = false
}

It is not possible to generate the setter function due to a Xtext limitation. Indeed, the generated setter may be:

public void setThevar(<<INFERENCED TYPE>> thevar) {
  this.thevar = thevar;
}

Unfortunately, for generating the method setThevar Xtext needs to kwow all the properties of the formal parameters. But, the inferred type cannot be determine because the inferring engine is not reflexive. See https://bugs.eclipse.org/bugs/show_bug.cgi?id=408323.

[gallandarakhneorg]

The only way to provide access to the attributes from the subclasses of agents is to make protected the attributes. The getter/setter becomes not more required.