RE: JESS: Is it possible to bind a Java object directly to a Jess variable without creating a new object?

[Friedman-Hill, Ernest]

That's what Rete.add() and Rete.definstance() do. If that's the goal, all of 
this other stuff is superfluous -- just call add() or definstance() from Java.

________________________________
From: owner-jess-us...@sandia.gov [mailto:owner-jess-us...@sandia.gov] On 
Behalf Of Hunter McMillen
Sent: Friday, November 04, 2011 7:50 PM
To: jess-users
Subject: Re: JESS: Is it possible to bind a Java object directly to a Jess 
variable without creating a new object?

Thanks for your quick reply. After I manage to get my Java object into Jess, 
can I assert it as a fact? Then have rules lhs match on the existence of some 
object with attributes x, y, and z?

Hunter

On Fri, Nov 4, 2011 at 4:01 PM, Friedman-Hill, Ernest 
<ejfr...@sandia.gov<mailto:ejfr...@sandia.gov>> wrote:
There are (obviously) two options: (a) put the object somewhere accessible, and 
run Jess code that retrieves it, or (b) use Jess's Java API to set a Jess 
variable to contain the object. Either would work. The store/fetch mechanism is 
sort of an built-in easy way to do (a). Alternatively, say there's a global 
variable ?*x* defined in your Jess program. Then you can say

engine.getGlobalContext().setVariable("*x*", new Value(unit));

and your Jess code can later get the value of "*x*".

If you don't like using variables this way, there's always directly invoking 
Jess functions from Java. Here we invoke 'add' to add the object to working 
memory directly:

new Funcall("add", engine).arg(new 
Value(unit)).execute(engine.getGlobalContext());


________________________________
From: owner-jess-us...@sandia.gov<mailto:owner-jess-us...@sandia.gov> 
[mailto:owner-jess-us...@sandia.gov<mailto:owner-jess-us...@sandia.gov>] On 
Behalf Of Hunter McMillen
Sent: Friday, November 04, 2011 1:08 PM
To: jess-users
Subject: JESS: Is it possible to bind a Java object directly to a Jess variable 
without creating a new object?

Hi everyone,

I am trying to assert to Jess that an object exists when I encounter a new 
object in my Java program. Right now I am using a template to mirror that 
object (i.e I have slot values for all of the Java objects fields)  but this 
seems redundant to me. Is there any way to just bind a Java object to a Jess 
variable without creating a new Java object?

A lot of the examples I see online and from JIA are of the form:
(bind ?map (new HashMap))

or

(call Classname method params...)

but these either create  a new object or call static methods. I already have 
the Java object and just want to store it.

But I was hoping that there was someway I could do something like this:
public Rete engine = new Rete();

public void unitDiscovered()
{
    Unit unit = <some unit encountered>; //Java object
    engine.executeCommand("(bind ?unit unit)");
    engine.executeCommand("(assert ?unit)");
}

Or would I have to use the store() and fetch() methods for this?

public void unitDiscovered()
{
    Unit unit = <some unit encountered>; //Java object
    engine.store("UNIT", unit);
    engine.executeCommand("(bind ?unit (fetch "UNIT")");
    engine.executeCommand("(assert ?unit)");
}

Basically I want to know the best practice for binding Java objects to Jess 
variables so I can assert them to the engine.

Thanks,
Hunter McMillen