A creates-->B,C. B call-> A call-> C?

I hope I am missing something obvious here:

Say I have three objects A, B, and C. My program starts with object "A".
I use object "A" to create instances of objects "B" and "C". Object "B"
does some work and when "B" completes its work, I want it to raise an event
that object "A" can see so that object "A" can respond by making object "C"
do some work.

How can I enable object B to effectively call a method in object A (by raising
an event or something) so that object A can in turn call a method in object
C?

I've learned that object B can call a static method in object A. But the
rule for static methods is that they can only operate on the class to which
they belong (meaning that a static method in object A could not call a method
in object C).

You see, objects "B" and "C" do specialized work as all good objects should
do. But I need object "A" to be able to coordintate the activities between
"B" and "C".

How do I handle this?

I hope you are too.

First of all, object B doesn't "do some work". But a method of object B
does do some work. So when object A calls that method, the method does the
work, whatever it is. After that, object A is free to do whatever it is
programmed to, such as calling a method in object C.

Here's a fragment of code that might be in object A:

B.doSomething(); // B does something
C.doAnotherThing(); // then C does something

It's really very simple. Don't try to make it complicated.

PC2

rneal <rneal@imseries.com> wrote in message news:3a357f71$1@news.devx.com...
>
> I hope I am missing something obvious here:
>
> Say I have three objects A, B, and C. My program starts with object "A".
> I use object "A" to create instances of objects "B" and "C". Object "B"
> does some work and when "B" completes its work, I want it to raise an
event
> that object "A" can see so that object "A" can respond by making object
"C"
> do some work.
>
> How can I enable object B to effectively call a method in object A (by
raising
> an event or something) so that object A can in turn call a method in
object
> C?
>
> I've learned that object B can call a static method in object A. But the
> rule for static methods is that they can only operate on the class to
which
> they belong (meaning that a static method in object A could not call a
method
> in object C).
>
> You see, objects "B" and "C" do specialized work as all good objects
should
> do. But I need object "A" to be able to coordintate the activities
between
> "B" and "C".
>
> How do I handle this?

The best approach to this kind of problems is use of interfaces. If you remember
the GUI event hadling you can approach your problem in the same manner.

In class B have a method something like addXXXListener() and in B store all
the handlers. When you are done with B invoke method on all handlers. I
am giving a sample skelton.

public interface MyOwnListener
{
public void inovkeme();
}

public class B
{
ArrayList listeners = new ArrayList(5);

public void addMyOwnListener(MyOwnListener l)
{
if(l != null)
listeners.add(l);
}

public void removeListener(MyOwnListener l)
{
if(l != null)
listeners.remove(l);
}

// Whe you are done with B call invokeme on all listeners.
public void done()
{
for(final Iterator ite=listeners.iterator(); ite.hasNext();
{
MyOwnListener l = (MyOwnListener)ite.next();
l.invokeme();
}
}
}

public class A implements MyOwnListener
{

public A()
{
B b = new B();
b.addMyOwnListener(this);
}


//Invoke when B is done.
public void invokeme()
{
C c = new C();
}
}



"rneal" <rneal@imseries.com> wrote:
>
>I hope I am missing something obvious here:
>
>Say I have three objects A, B, and C. My program starts with object "A".
> I use object "A" to create instances of objects "B" and "C". Object "B"
>does some work and when "B" completes its work, I want it to raise an event
>that object "A" can see so that object "A" can respond by making object
"C"
>do some work.
>
>How can I enable object B to effectively call a method in object A (by raising
>an event or something) so that object A can in turn call a method in object
>C?
>
>I've learned that object B can call a static method in object A. But the
>rule for static methods is that they can only operate on the class to which
>they belong (meaning that a static method in object A could not call a method
>in object C).
>
>You see, objects "B" and "C" do specialized work as all good objects should
>do. But I need object "A" to be able to coordintate the activities between
>"B" and "C".
>
>How do I handle this?